Filed by County Bancorp, Inc. Pursuant to Rule 425 under the Securities Act of 1933, as amended and deemed filed pursuant to Rule 14a-12 Working with Marketing on new style & color scheme throughout under the Securities Exchange Act of 1934, as amended Subject Company: County Bancorp, Inc. (Commission File No. 001-36808) Date: June 22, 2021 Acquisition of County Bancorp, Inc. June 22, 2021Filed by County Bancorp, Inc. Pursuant to Rule 425 under the Securities Act of 1933, as amended and deemed filed pursuant to Rule 14a-12 Working with Marketing on new style & color scheme throughout under the Securities Exchange Act of 1934, as amended Subject Company: County Bancorp, Inc. (Commission File No. 001-36808) Date: June 22, 2021 Acquisition of County Bancorp, Inc. June 22, 2021

Securities Legend Forward Looking Statements “Safe Harbor” Statement Under the Private Securities Litigation Reform Act of 1995 Certain statements contained in this communication, which are not statements of historical fact, constitute forward-looking statements within the meaning of the federal securities law. Such statements include, but are not limited to, certain plans, expectations, goals, projections and benefits relating to the proposed merger between Nicolet and County, as well as expectations regarding Nicolet’s proposed acquisition of Mackinac Financial Corporation (“Mackinac”), all of which are subject to numerous assumptions, risks and uncertainties. Words or phrases such as “anticipate,” “believe,” “aim,” “can,” “conclude,” “continue,” “could,” “estimate,” “expect,” “foresee,” “goal,” “intend,” “may,” “might,” “outlook,” “possible,” “plan,” “predict,” “project,” “potential,” “seek,” “should,” “target,” “will,” “will likely,” “would,” or the negative of these terms or other comparable terminology, as well as similar expressions, are intended to identify forward-looking statements but are not the exclusive means of identifying such statements. Forward-looking statements are not historical facts but instead express only management’s beliefs regarding future results or events, many of which, by their nature, are inherently uncertain and outside of management’s control. It is possible that actual results and outcomes may differ, possibly materially, from the anticipated results or outcomes indicated in these forward-looking statements. In addition to factors disclosed in reports filed by Nicolet and County with the SEC, risks and uncertainties for Nicolet, County and the combined company that may cause actual results or outcomes to differ materially from those anticipated include, but are not limited to: (1) the possibility that any of the anticipated benefits of the proposed merger will not be realized or will not be realized within the expected time period; (2) the risk that integration of County’s operations with those of Nicolet will be materially delayed or will be more costly or difficult than expected; (3) the parties’ inability to meet expectations regarding the timing of the proposed merger; (4) changes to tax legislation and their potential effects on the accounting for the merger; (5) the inability to complete the proposed merger due to the failure of Nicolet’s or County’s shareholders to adopt the Merger Agreement; (6) the failure to satisfy other conditions to completion of the proposed merger, including receipt of required regulatory and other approvals; (7) the failure of the proposed merger to close for any other reason; (8) diversion of management's attention from ongoing business operations and opportunities due to the proposed merger; (9) the challenges of integrating and retaining key employees; (10) the effect of the announcement of the proposed merger on Nicolet’s, County’s or the combined company’s respective customer and employee relationships and operating results; (11) the possibility that the proposed merger may be more expensive to complete than anticipated, including as a result of unexpected factors or events; (12) dilution caused by Nicolet’s issuance of additional shares of Nicolet common stock in connection with the merger; (13) risks and uncertainties relating to Nicolet’s proposed acquisition of Mackinac, including but not limited to the failure of the proposed acquisition to close for any reason and risks and uncertainties relating to the Mackinac’s business, the combined business of Mackinac and Nicolet, and the combined businesses of Nicolet, County and Mackinac; (14) the magnitude and duration of the COVID-19 pandemic and its impact on the global economy and financial market conditions and the business, results of operations and financial condition of Nicolet, County and the combined company; (15) changes in consumer demand for financial services; and (16) general competitive, economic, political and market conditions and fluctuations. Please refer to each of Nicolet’s, County’s and Mackinac’s Annual Report on Form 10-K for the year ended December 31, 2020, as well as their other filings with the SEC, for a more detailed discussion of risks, uncertainties and factors that could cause actual results to differ from those discussed in the forward-looking statements. All forward-looking statements included in this communication are made as of the date hereof and are based on information available to management at that time. Except as required by law, neither Nicolet nor County assumes any obligation to update any forward-looking statement to reflect events or circumstances that occur after the date the forward-looking statements were made.Securities Legend Forward Looking Statements “Safe Harbor” Statement Under the Private Securities Litigation Reform Act of 1995 Certain statements contained in this communication, which are not statements of historical fact, constitute forward-looking statements within the meaning of the federal securities law. Such statements include, but are not limited to, certain plans, expectations, goals, projections and benefits relating to the proposed merger between Nicolet and County, as well as expectations regarding Nicolet’s proposed acquisition of Mackinac Financial Corporation (“Mackinac”), all of which are subject to numerous assumptions, risks and uncertainties. Words or phrases such as “anticipate,” “believe,” “aim,” “can,” “conclude,” “continue,” “could,” “estimate,” “expect,” “foresee,” “goal,” “intend,” “may,” “might,” “outlook,” “possible,” “plan,” “predict,” “project,” “potential,” “seek,” “should,” “target,” “will,” “will likely,” “would,” or the negative of these terms or other comparable terminology, as well as similar expressions, are intended to identify forward-looking statements but are not the exclusive means of identifying such statements. Forward-looking statements are not historical facts but instead express only management’s beliefs regarding future results or events, many of which, by their nature, are inherently uncertain and outside of management’s control. It is possible that actual results and outcomes may differ, possibly materially, from the anticipated results or outcomes indicated in these forward-looking statements. In addition to factors disclosed in reports filed by Nicolet and County with the SEC, risks and uncertainties for Nicolet, County and the combined company that may cause actual results or outcomes to differ materially from those anticipated include, but are not limited to: (1) the possibility that any of the anticipated benefits of the proposed merger will not be realized or will not be realized within the expected time period; (2) the risk that integration of County’s operations with those of Nicolet will be materially delayed or will be more costly or difficult than expected; (3) the parties’ inability to meet expectations regarding the timing of the proposed merger; (4) changes to tax legislation and their potential effects on the accounting for the merger; (5) the inability to complete the proposed merger due to the failure of Nicolet’s or County’s shareholders to adopt the Merger Agreement; (6) the failure to satisfy other conditions to completion of the proposed merger, including receipt of required regulatory and other approvals; (7) the failure of the proposed merger to close for any other reason; (8) diversion of management's attention from ongoing business operations and opportunities due to the proposed merger; (9) the challenges of integrating and retaining key employees; (10) the effect of the announcement of the proposed merger on Nicolet’s, County’s or the combined company’s respective customer and employee relationships and operating results; (11) the possibility that the proposed merger may be more expensive to complete than anticipated, including as a result of unexpected factors or events; (12) dilution caused by Nicolet’s issuance of additional shares of Nicolet common stock in connection with the merger; (13) risks and uncertainties relating to Nicolet’s proposed acquisition of Mackinac, including but not limited to the failure of the proposed acquisition to close for any reason and risks and uncertainties relating to the Mackinac’s business, the combined business of Mackinac and Nicolet, and the combined businesses of Nicolet, County and Mackinac; (14) the magnitude and duration of the COVID-19 pandemic and its impact on the global economy and financial market conditions and the business, results of operations and financial condition of Nicolet, County and the combined company; (15) changes in consumer demand for financial services; and (16) general competitive, economic, political and market conditions and fluctuations. Please refer to each of Nicolet’s, County’s and Mackinac’s Annual Report on Form 10-K for the year ended December 31, 2020, as well as their other filings with the SEC, for a more detailed discussion of risks, uncertainties and factors that could cause actual results to differ from those discussed in the forward-looking statements. All forward-looking statements included in this communication are made as of the date hereof and are based on information available to management at that time. Except as required by law, neither Nicolet nor County assumes any obligation to update any forward-looking statement to reflect events or circumstances that occur after the date the forward-looking statements were made.

Securities Legend Important Information and Where to Find It This communication relates to the proposed merger transaction involving Nicolet and County. In connection with the proposed merger, Nicolet and County will file a joint proxy statement/prospectus on Form S-4 and other relevant documents concerning the merger with the Securities and Exchange Commission (the “SEC”). BEFORE MAKING ANY VOTING OR INVESTMENT DECISION, INVESTORS ARE URGED TO READ THE JOINT PROXY STATEMENT/PROSPECTUS AND ANY OTHER DOCUMENTS TO BE FILED WITH THE SEC IN CONNECTION WITH THE PROPOSED MERGER OR INCORPORATED BY REFERENCE IN THE JOINT PROXY STATEMENT/PROSPECTUS BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT NICOLET, COUNTY AND THE PROPOSED MERGER. When available, the joint proxy statement/prospectus will be delivered to shareholders of Nicolet and County. Investors may obtain copies of the joint proxy statement/prospectus and other relevant documents (as they become available) free of charge at the SEC’s website (www.sec.gov). Copies of the documents filed with the SEC by Nicolet will be available free of charge on Nicolet’s website at www.nicoletbank.com. Copies of the documents filed with the SEC by County will be available free of charge on County’s website at investors.ICBK.com/documents. Nicolet, County and certain of their directors, executive officers and other members of management and employees may be deemed to be participants in the solicitation of proxies from the shareholders of Nicolet and the shareholders of County in connection with the proposed merger. Information about the directors and executive officers of Nicolet and County will be included in the joint proxy statement/prospectus for the proposed transaction filed with the SEC. Information about the directors and executive officers of Nicolet is also included in the proxy statement for its 2021 annual meeting of shareholders, which was filed with the SEC on March 2, 2021. Information about the directors and executive officers of County is also included in the proxy statement for its 2021 annual meeting of shareholders, which was filed with the SEC on April 5, 2021. Additional information regarding the interests of such participants and other persons who may be deemed participants in the transaction will be included in the joint proxy statement/prospectus and the other relevant documents filed with the SEC when they become available. No Offer or Solicitation This communication shall not constitute an offer to sell or the solicitation of an offer to sell or the solicitation of an offer to buy any securities, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation, or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offer of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended.Securities Legend Important Information and Where to Find It This communication relates to the proposed merger transaction involving Nicolet and County. In connection with the proposed merger, Nicolet and County will file a joint proxy statement/prospectus on Form S-4 and other relevant documents concerning the merger with the Securities and Exchange Commission (the “SEC”). BEFORE MAKING ANY VOTING OR INVESTMENT DECISION, INVESTORS ARE URGED TO READ THE JOINT PROXY STATEMENT/PROSPECTUS AND ANY OTHER DOCUMENTS TO BE FILED WITH THE SEC IN CONNECTION WITH THE PROPOSED MERGER OR INCORPORATED BY REFERENCE IN THE JOINT PROXY STATEMENT/PROSPECTUS BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT NICOLET, COUNTY AND THE PROPOSED MERGER. When available, the joint proxy statement/prospectus will be delivered to shareholders of Nicolet and County. Investors may obtain copies of the joint proxy statement/prospectus and other relevant documents (as they become available) free of charge at the SEC’s website (www.sec.gov). Copies of the documents filed with the SEC by Nicolet will be available free of charge on Nicolet’s website at www.nicoletbank.com. Copies of the documents filed with the SEC by County will be available free of charge on County’s website at investors.ICBK.com/documents. Nicolet, County and certain of their directors, executive officers and other members of management and employees may be deemed to be participants in the solicitation of proxies from the shareholders of Nicolet and the shareholders of County in connection with the proposed merger. Information about the directors and executive officers of Nicolet and County will be included in the joint proxy statement/prospectus for the proposed transaction filed with the SEC. Information about the directors and executive officers of Nicolet is also included in the proxy statement for its 2021 annual meeting of shareholders, which was filed with the SEC on March 2, 2021. Information about the directors and executive officers of County is also included in the proxy statement for its 2021 annual meeting of shareholders, which was filed with the SEC on April 5, 2021. Additional information regarding the interests of such participants and other persons who may be deemed participants in the transaction will be included in the joint proxy statement/prospectus and the other relevant documents filed with the SEC when they become available. No Offer or Solicitation This communication shall not constitute an offer to sell or the solicitation of an offer to sell or the solicitation of an offer to buy any securities, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation, or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offer of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended.

The Upper Midwest’s Premier Community Bank + Additional Scale. Creates the second largest bank \ headquartered and the #1 bank lending to the dairy industry in the state of Wisconsin Diversification. County’s ag portfolio provides additional diversification to Nicolet, comprising roughly 15% of the pro (1) forma loan portfolio Nicolet County Shared Entrepreneurial Cultures. Founded three years Mackinac apart in 1997 and 2000, both County and Nicolet operate with nd an entrepreneurial culture and are led by the original founders 2 Largest that have known and respected each over the last couple of Bank headquartered in Wisconsin decades #1 Bank Lender Complements Mackinac Transaction. County’s leading to the dairy industry in Wisconsin market position in the dairy sector along with Nicolet’s low-cost core deposit funding base will allow for the deployment of excess liquidity and be a source for future growth #1 Market Share (2) in Michigan’s Upper Peninsula Top Tier Performance. Nicolet’s history of providing consistent EPS growth, strong ROAA, and top quartile ROATCE #9 Ranked will be further enhanced by the EPS accretion expected in 2022 and beyond with County and Mackinac among S&P Global’s “Best Performing Community (3) Banks of 2020” (1) Nicolet pro forma with Mackinac – see page 8 for detail (2) Based on S&P Global Market Intelligence deposit market share information as of 6/30/20 for all 15 counties in the Upper Peninsula 4 (3) S&P Global Market Intelligence - Includes banks $3 to $10 billion in total assets as of 12/31/20The Upper Midwest’s Premier Community Bank + Additional Scale. Creates the second largest bank \ headquartered and the #1 bank lending to the dairy industry in the state of Wisconsin Diversification. County’s ag portfolio provides additional diversification to Nicolet, comprising roughly 15% of the pro (1) forma loan portfolio Nicolet County Shared Entrepreneurial Cultures. Founded three years Mackinac apart in 1997 and 2000, both County and Nicolet operate with nd an entrepreneurial culture and are led by the original founders 2 Largest that have known and respected each over the last couple of Bank headquartered in Wisconsin decades #1 Bank Lender Complements Mackinac Transaction. County’s leading to the dairy industry in Wisconsin market position in the dairy sector along with Nicolet’s low-cost core deposit funding base will allow for the deployment of excess liquidity and be a source for future growth #1 Market Share (2) in Michigan’s Upper Peninsula Top Tier Performance. Nicolet’s history of providing consistent EPS growth, strong ROAA, and top quartile ROATCE #9 Ranked will be further enhanced by the EPS accretion expected in 2022 and beyond with County and Mackinac among S&P Global’s “Best Performing Community (3) Banks of 2020” (1) Nicolet pro forma with Mackinac – see page 8 for detail (2) Based on S&P Global Market Intelligence deposit market share information as of 6/30/20 for all 15 counties in the Upper Peninsula 4 (3) S&P Global Market Intelligence - Includes banks $3 to $10 billion in total assets as of 12/31/20

Transaction Highlights & Rationale § Establishes Nicolet as #1 Banking Dairy Lender in the state of Wisconsin § Creates an additional niche business line that further diversifies Nicolet’s existing loan portfolio and can be scaled and fully funded using Nicolet’s excess liquidity Strategic § Creates a $7.5 billion community banking franchise – one of the largest focused Rationale exclusively on the Upper Midwest § Enhances scale in existing markets of Green Bay and Appleton (1) (2) § EPS accretion in mid-single digits in 2022 (1) (3) Positive § Tangible book value dilution of approximately 1.2%, with an earnback of 1.4 years Financial § Internal rate of return > 20% Impacts § Identified, but no modeled revenue enhancements (including mortgage and wealth management) § Ability to leverage Nicolet’s larger balance sheet and existing diversified loan portfolio to fund larger portion of agricultural lending opportunities (County currently participates a large percentage of newly originated ag credits due to funding issues) Revenue § Opportunity to bring portion of County’s $842 million ag servicing book back on balance Opportunities sheet over time § Immediate ability to utilize Nicolet’s excess liquidity and cash position to reduce County’s (4) funding costs (including $135 million in callable CDs and other higher cost funding) (1) Nicolet presented pro forma for announced acquisition of Mackinac Financial Corporation (2) Assumes 100% phase-in of cost savings 5 (3) Crossover method (4) ICBK company reportsTransaction Highlights & Rationale § Establishes Nicolet as #1 Banking Dairy Lender in the state of Wisconsin § Creates an additional niche business line that further diversifies Nicolet’s existing loan portfolio and can be scaled and fully funded using Nicolet’s excess liquidity Strategic § Creates a $7.5 billion community banking franchise – one of the largest focused Rationale exclusively on the Upper Midwest § Enhances scale in existing markets of Green Bay and Appleton (1) (2) § EPS accretion in mid-single digits in 2022 (1) (3) Positive § Tangible book value dilution of approximately 1.2%, with an earnback of 1.4 years Financial § Internal rate of return > 20% Impacts § Identified, but no modeled revenue enhancements (including mortgage and wealth management) § Ability to leverage Nicolet’s larger balance sheet and existing diversified loan portfolio to fund larger portion of agricultural lending opportunities (County currently participates a large percentage of newly originated ag credits due to funding issues) Revenue § Opportunity to bring portion of County’s $842 million ag servicing book back on balance Opportunities sheet over time § Immediate ability to utilize Nicolet’s excess liquidity and cash position to reduce County’s (4) funding costs (including $135 million in callable CDs and other higher cost funding) (1) Nicolet presented pro forma for announced acquisition of Mackinac Financial Corporation (2) Assumes 100% phase-in of cost savings 5 (3) Crossover method (4) ICBK company reports

County Bancorp Financial Highlights & Market Overview County Bancorp Market Overview County Financial Branch Map • #1 Banking dairy lender in the state of Wisconsin with WI Counties with lending relationships in 55 of the state’s 72 counties lending relationships • Strong local presence in home market of Manitowoc and Full Service Branch lead local community bank in Stevens Point MSA • LPO locations in Eau Claire, Sheboygan, Fond du Lac, and Loan Production Office Darlington service state-wide client footprint • Lenders & support staff located throughout the state of Wisconsin support highly personalized customer service and understanding of localized industry trends with emphasis on the consolidating family-owned dairy sector Manitowoc & Stevens Point MSA (2) County Summary Financials (1) Deposit Market Share 2018 2019 2020 2021 Q1 Deposits In Market Total Assets $1,521,027 $1,378,779 $1,472,358 $1,491,328 Asset Growth 8.9% -9.4% 6.8% 1.3% Rank Institution Branches Market ($M) Share Total Net Loans $1,193,739 $1,022,657 $1,017,453 $1,002,370 1 Bank First Corporation 7 $692 34.5% Loan Growth 4.5% -14.3% -0.5% -1.5% 2 County Bancorp Inc. 1 $644 32.1% Total Deposits $1,223,347 $1,101,442 $1,040,826 $1,098,528 3 Associated Banc-Corp 3 $242 12.1% Deposit Growth 10.2% -10.0% -5.5% 5.5% 4 U.S. Bancorp 2 $119 5.9% Loans / Deposits 99% 94% 96% 92% Equity / Assets 9.68% 12.14% 11.66% 11.15% 5 Denmark Bancshares Inc. 2 $91 4.6% ------------------------------- Total For 9 Institutions In Market 21 $2,004 Net Income $14,251 $16,452 $5,479 $3,928 Deposits In Market ROAA 0.96% 1.13% 0.38% 1.06% ROAE 9.50% 10.10% 3.22% 9.11% Rank Institution Branches Market ($M) Share Net Interest Margin 2.91% 2.93% 2.68% 2.95% 1 Bank of Montreal 3 $881 42.3% Efficiency Ratio 52.7% 56.7% 65.3% 62.4% 2 Associated Banc-Corp 4 $218 10.5% ------------------------------- 3 JPMorgan Chase & Co. 1 $177 8.5% NPAs/ Assets 3.22% 4.23% 4.16% 3.90% NCOs/ Avg Loans -0.01% 0.15% 0.32% -0.01% 4 County Bancorp Inc. 1 $174 8.4% LLR / Loans 1.36% 1.47% 1.43% 1.48% 5 Portage County Bancshares Inc. 4 $105 5.0% Total For 14 Institutions In Market 24 $2,082 (1) Source: S&P Global Market Intelligence as of June 30, 2020 (2) Source: S&P Global Market Intelligence / Company Reports; 2020 financials include one-time goodwill impairment charge of 6 $5.0 million Stevens Point MSA Manitowoc MSACounty Bancorp Financial Highlights & Market Overview County Bancorp Market Overview County Financial Branch Map • #1 Banking dairy lender in the state of Wisconsin with WI Counties with lending relationships in 55 of the state’s 72 counties lending relationships • Strong local presence in home market of Manitowoc and Full Service Branch lead local community bank in Stevens Point MSA • LPO locations in Eau Claire, Sheboygan, Fond du Lac, and Loan Production Office Darlington service state-wide client footprint • Lenders & support staff located throughout the state of Wisconsin support highly personalized customer service and understanding of localized industry trends with emphasis on the consolidating family-owned dairy sector Manitowoc & Stevens Point MSA (2) County Summary Financials (1) Deposit Market Share 2018 2019 2020 2021 Q1 Deposits In Market Total Assets $1,521,027 $1,378,779 $1,472,358 $1,491,328 Asset Growth 8.9% -9.4% 6.8% 1.3% Rank Institution Branches Market ($M) Share Total Net Loans $1,193,739 $1,022,657 $1,017,453 $1,002,370 1 Bank First Corporation 7 $692 34.5% Loan Growth 4.5% -14.3% -0.5% -1.5% 2 County Bancorp Inc. 1 $644 32.1% Total Deposits $1,223,347 $1,101,442 $1,040,826 $1,098,528 3 Associated Banc-Corp 3 $242 12.1% Deposit Growth 10.2% -10.0% -5.5% 5.5% 4 U.S. Bancorp 2 $119 5.9% Loans / Deposits 99% 94% 96% 92% Equity / Assets 9.68% 12.14% 11.66% 11.15% 5 Denmark Bancshares Inc. 2 $91 4.6% ------------------------------- Total For 9 Institutions In Market 21 $2,004 Net Income $14,251 $16,452 $5,479 $3,928 Deposits In Market ROAA 0.96% 1.13% 0.38% 1.06% ROAE 9.50% 10.10% 3.22% 9.11% Rank Institution Branches Market ($M) Share Net Interest Margin 2.91% 2.93% 2.68% 2.95% 1 Bank of Montreal 3 $881 42.3% Efficiency Ratio 52.7% 56.7% 65.3% 62.4% 2 Associated Banc-Corp 4 $218 10.5% ------------------------------- 3 JPMorgan Chase & Co. 1 $177 8.5% NPAs/ Assets 3.22% 4.23% 4.16% 3.90% NCOs/ Avg Loans -0.01% 0.15% 0.32% -0.01% 4 County Bancorp Inc. 1 $174 8.4% LLR / Loans 1.36% 1.47% 1.43% 1.48% 5 Portage County Bancshares Inc. 4 $105 5.0% Total For 14 Institutions In Market 24 $2,082 (1) Source: S&P Global Market Intelligence as of June 30, 2020 (2) Source: S&P Global Market Intelligence / Company Reports; 2020 financials include one-time goodwill impairment charge of 6 $5.0 million Stevens Point MSA Manitowoc MSA

Leading Deposit Market Share in WI and Upper Peninsula Pro Forma Branch Map: Nicolet branches (36) County branches (4) Mackinac branches (28) Note: Map does not include County’s loan production offices in Eau Claire, Sheboygan, Fond du Lac, and Darlington, Wisconsin 7Leading Deposit Market Share in WI and Upper Peninsula Pro Forma Branch Map: Nicolet branches (36) County branches (4) Mackinac branches (28) Note: Map does not include County’s loan production offices in Eau Claire, Sheboygan, Fond du Lac, and Darlington, Wisconsin 7

A Leading Business Bank in its Markets Nicolet - $3.9B Combined - $4.9B County - $1.0B Consumer Ag Consumer Residential RE Ag 1.2% 2.8% 1.0% Ag 14.6% 20.2% Const & Land 60.0% Const & Land Const & Land Residential RE 5.8% 4.9% 1.3% 16.8% C&I Commercial RE - 11.7% Owner Occ 18.5% Commercial RE - C&I Commercial RE - Owner Occ C&I 27.4% Investment 16.4% 31.5% 14.8% Commercial RE - Commercial RE - Investment Investment 19.9% Commercial RE - Residential RE 18.9% Owner Occ 3.7% 8.4% MRQ Yield = 4.92% MRQ Yield = 4.64% Combined MRQ Yield = 4.86% County - $1.1B Combined - $6.3B Nicolet - $5.2B Noninterest Bearing Noninterest Noninterest Bearing 32.1% Bearing MMA & 12.7% 28.7% Interest-bearing Customer CDs demand Customer CDs 9.9% 44.3% 12.6% MMA & Interest-bearing Brokered MMA & Customer CDs demand 5.3% 25.4% Brokered Interest-bearing 39.9% 7.3% demand 39.0% Savings Savings 11.4% Savings 13.7% Brokered 0.8% 16.9% MRQ Cost = 0.30% MRQ Cost = 0.78% Combined MRQ Cost = 0.38% Source: S&P Global and internal company reports as of March 31, 2021 Note: Nicolet pro forma with Mackinac Financial Corporation, including combined MRQ loan yield and deposit costs as of 8 March 31, 2021 Deposit Portfolio Loan PortfolioA Leading Business Bank in its Markets Nicolet - $3.9B Combined - $4.9B County - $1.0B Consumer Ag Consumer Residential RE Ag 1.2% 2.8% 1.0% Ag 14.6% 20.2% Const & Land 60.0% Const & Land Const & Land Residential RE 5.8% 4.9% 1.3% 16.8% C&I Commercial RE - 11.7% Owner Occ 18.5% Commercial RE - C&I Commercial RE - Owner Occ C&I 27.4% Investment 16.4% 31.5% 14.8% Commercial RE - Commercial RE - Investment Investment 19.9% Commercial RE - Residential RE 18.9% Owner Occ 3.7% 8.4% MRQ Yield = 4.92% MRQ Yield = 4.64% Combined MRQ Yield = 4.86% County - $1.1B Combined - $6.3B Nicolet - $5.2B Noninterest Bearing Noninterest Noninterest Bearing 32.1% Bearing MMA & 12.7% 28.7% Interest-bearing Customer CDs demand Customer CDs 9.9% 44.3% 12.6% MMA & Interest-bearing Brokered MMA & Customer CDs demand 5.3% 25.4% Brokered Interest-bearing 39.9% 7.3% demand 39.0% Savings Savings 11.4% Savings 13.7% Brokered 0.8% 16.9% MRQ Cost = 0.30% MRQ Cost = 0.78% Combined MRQ Cost = 0.38% Source: S&P Global and internal company reports as of March 31, 2021 Note: Nicolet pro forma with Mackinac Financial Corporation, including combined MRQ loan yield and deposit costs as of 8 March 31, 2021 Deposit Portfolio Loan Portfolio

Dairy-Related Lending Niche Dairy Lending Origins High Personal Touch Model Credit & Risk Management Banking Dairy lender in Strong advisor / #1 #1 ü Wisconsin partnership model County’s Valuably Serving Local Markets Ever-evolving with the Industry A Securing the Following: Expertise All Notes Seasoned Ag. & Dairy Expanding lending • Loans cross-collateralized with TBU lenders with extensive facilities to overcome ü ü pledged farm assets sector knowledge consolidation trends Operating Lines of Credit + • Inventory and growing crops Significant Excess Liquidity Loan Origination Potential pledged as collateral Cash & C.E.-to-Assets Higher anticipated Intermediate Term Loans 17% ü Legal Lending Limit• Secured by pledged Nicolet’s (1) Loan-to-Deposits equipment and livestock 76% Balance Sheet B & Credit Long Term Loans Low Funding Costs Strong Credit Culture • Secured by pledged farm real Culture estate assets Cost of deposits on History of low 30bps (1) ü $5.1B in deposits charge-offs Highlights: = Full Relationship Wisconsin Dairy Exports Have Nicolet Adds a New • Generally sole lender on the Grown in Each of Last 4 Years Major Business Line leading farms that have scale 7,000+ Dairy Farms in WI Ag. Comm. and strong management / Long-term owners C Cheese producer in US Wealth #1 Retail Opportunity Farm Service Agency (“FSA”) nd • 2 leading originator of FSA Future growth by In off balance sheet government-guaranteed loan $842M bringing a portion on servicing portfolio (ICB) program in the country balance sheet over time (1) Nicolet pro forma with Mackinac Financial Corporation as of March 31, 2021 9Dairy-Related Lending Niche Dairy Lending Origins High Personal Touch Model Credit & Risk Management Banking Dairy lender in Strong advisor / #1 #1 ü Wisconsin partnership model County’s Valuably Serving Local Markets Ever-evolving with the Industry A Securing the Following: Expertise All Notes Seasoned Ag. & Dairy Expanding lending • Loans cross-collateralized with TBU lenders with extensive facilities to overcome ü ü pledged farm assets sector knowledge consolidation trends Operating Lines of Credit + • Inventory and growing crops Significant Excess Liquidity Loan Origination Potential pledged as collateral Cash & C.E.-to-Assets Higher anticipated Intermediate Term Loans 17% ü Legal Lending Limit• Secured by pledged Nicolet’s (1) Loan-to-Deposits equipment and livestock 76% Balance Sheet B & Credit Long Term Loans Low Funding Costs Strong Credit Culture • Secured by pledged farm real Culture estate assets Cost of deposits on History of low 30bps (1) ü $5.1B in deposits charge-offs Highlights: = Full Relationship Wisconsin Dairy Exports Have Nicolet Adds a New • Generally sole lender on the Grown in Each of Last 4 Years Major Business Line leading farms that have scale 7,000+ Dairy Farms in WI Ag. Comm. and strong management / Long-term owners C Cheese producer in US Wealth #1 Retail Opportunity Farm Service Agency (“FSA”) nd • 2 leading originator of FSA Future growth by In off balance sheet government-guaranteed loan $842M bringing a portion on servicing portfolio (ICB) program in the country balance sheet over time (1) Nicolet pro forma with Mackinac Financial Corporation as of March 31, 2021 9

Comprehensive Due Diligence Process Ø Nicolet is an experienced acquirer having announced seven bank acquisitions since 2013 Ø Long track record of earnings and tangible book value growth Disciplined Acquirer Ø Historically out-performed initial cost savings estimates Ø Concurrent close & convert model allows for the bulk of cost savings to be immediately realized Ø Collaborative process lasting approximately 30 days Holistic Diligence Ø Nicolet’s experienced credit diligence team (including its own ag lending team) reviewed a significant portion of the loan portfolio Approach Ø Preliminary review of personnel at both institutions Loan Review Process Diligence Focus Areas Corporate / Org. Third Party Doc.’s Extensive Loan Review Analysis Financial Human Resources Insurance 370+ Loan Portfolio $867 Million Ag & Commercial Total loan balance reviewed relationships reviewed Investment Portfolio Compliance Ø 93% of all ag related relationships ALM Mortgage Banking Ø 85% of all commercial relationships Deposits / Funding Branches / Facilities Ø 100% of adversely classified assets and Watch List credits Ø The retail loan portfolio based on payment performance 10Comprehensive Due Diligence Process Ø Nicolet is an experienced acquirer having announced seven bank acquisitions since 2013 Ø Long track record of earnings and tangible book value growth Disciplined Acquirer Ø Historically out-performed initial cost savings estimates Ø Concurrent close & convert model allows for the bulk of cost savings to be immediately realized Ø Collaborative process lasting approximately 30 days Holistic Diligence Ø Nicolet’s experienced credit diligence team (including its own ag lending team) reviewed a significant portion of the loan portfolio Approach Ø Preliminary review of personnel at both institutions Loan Review Process Diligence Focus Areas Corporate / Org. Third Party Doc.’s Extensive Loan Review Analysis Financial Human Resources Insurance 370+ Loan Portfolio $867 Million Ag & Commercial Total loan balance reviewed relationships reviewed Investment Portfolio Compliance Ø 93% of all ag related relationships ALM Mortgage Banking Ø 85% of all commercial relationships Deposits / Funding Branches / Facilities Ø 100% of adversely classified assets and Watch List credits Ø The retail loan portfolio based on payment performance 10

Transaction Overview and Assumptions • 0.48x shares of Nicolet OR $37.18 in cash for each share of County, subject to 80% stock / 20% consideration mix Transaction (1) • Total transaction value of $219 million Structure • County to merge with and into Nicolet; Investors Community Bank to merge with and into Nicolet National Bank • Cost Savings of 33% of County’s non interest expense base Synergies • 75% realized in 2022 and 100% thereafter • Total gross loan credit mark of 2.02%, or $19.5 million on net loan portfolio excluding PPP loans o 0.34%, or $3.3 million, non-PCD mark (amortized into earnings over the 3 year life of loans) Loan Credit Mark o 0.76%, or $7.3 million, PCD mark, recorded into ACL • Additional Day 2 CECL reserve of 0.92%, or $8.9 million; included in pro forma tangible book value at close • Net fair value write-down of $10.9 million on loans (interest rate), time deposits, trust preferred and subordinated debt Other Fair Value • Permanent balance sheet mark of $2.1 million pretax on fixed assets and OREO Estimates • Core deposit intangible of $3.2 million, amortized on an accelerated basis over 10 years • $19.0 million in estimated pretax deal related expenses Other Assumptions• Cash portion financed with new subordinated debt • One member of County’s Board will join the Boards of Directors of Nicolet Bankshares and Nicolet National Bank Management & • Tim Schneider (President of County) will join the senior management team of Nicolet as Senior Vice President, Board Agriculture Lending Manager • Anticipated close in fourth quarter 2021 Closing & • Subject to regulatory approvals, shareholder approvals by both Nicolet and County, and customary closing conditions Approvals (1) Market data as of June 21, 2021. Based on approximately 6.1 million County common shares outstanding (inclusive of County’s unvested restricted stock units) as of June 17, 2021. Inclusive of approximately $3.7 million for the cash-out value of County’s 11 stock optionsTransaction Overview and Assumptions • 0.48x shares of Nicolet OR $37.18 in cash for each share of County, subject to 80% stock / 20% consideration mix Transaction (1) • Total transaction value of $219 million Structure • County to merge with and into Nicolet; Investors Community Bank to merge with and into Nicolet National Bank • Cost Savings of 33% of County’s non interest expense base Synergies • 75% realized in 2022 and 100% thereafter • Total gross loan credit mark of 2.02%, or $19.5 million on net loan portfolio excluding PPP loans o 0.34%, or $3.3 million, non-PCD mark (amortized into earnings over the 3 year life of loans) Loan Credit Mark o 0.76%, or $7.3 million, PCD mark, recorded into ACL • Additional Day 2 CECL reserve of 0.92%, or $8.9 million; included in pro forma tangible book value at close • Net fair value write-down of $10.9 million on loans (interest rate), time deposits, trust preferred and subordinated debt Other Fair Value • Permanent balance sheet mark of $2.1 million pretax on fixed assets and OREO Estimates • Core deposit intangible of $3.2 million, amortized on an accelerated basis over 10 years • $19.0 million in estimated pretax deal related expenses Other Assumptions• Cash portion financed with new subordinated debt • One member of County’s Board will join the Boards of Directors of Nicolet Bankshares and Nicolet National Bank Management & • Tim Schneider (President of County) will join the senior management team of Nicolet as Senior Vice President, Board Agriculture Lending Manager • Anticipated close in fourth quarter 2021 Closing & • Subject to regulatory approvals, shareholder approvals by both Nicolet and County, and customary closing conditions Approvals (1) Market data as of June 21, 2021. Based on approximately 6.1 million County common shares outstanding (inclusive of County’s unvested restricted stock units) as of June 17, 2021. Inclusive of approximately $3.7 million for the cash-out value of County’s 11 stock options

Multiples and Pro Forma Impact Transaction Value / Tangible Book Value (3/31/2021)• 138% (1) Pay to Trade Ratio• 70% Transaction Value / LTM Earnings• 15.3x (2) Transaction Value / 2022E Earnings • 18.5x (2) (3) Transaction Value / 2022E Earnings + Synergies • 10.6x (4) Pro Forma with MFNC Standalone (2) Estimated 2022E EPS Accretion • 3.1%• 9.5% (75% Cost Savings Phase-In) (2) Estimated 2022E EPS Accretion • 5.4%• 12.7% (100% Cost Savings Phase-In) TBVPS Accretion / (Dilution)• (1.2%)• (1.9%) Tangible Book Value Earnback• 1.4 years• 1.4 years TCE / TA Ratio (estimated at close)• 8.2%• 8.5% CET1 Ratio (estimated at close) • 10.9%• 11.2% Internal Rate of Return• 20% + (1) Ratio of tangible book value multiple paid to Nicolet's tangible book value multiple as of June 21, 2021, presented pro forma for Nicolet's announced acquisition of Mackinac Financial Corporation (2) Based on mean consensus estimates 12 (3) Assumes 100% phase-in of cost savings (4) Nicolet and County combined; excludes impact of MFNCMultiples and Pro Forma Impact Transaction Value / Tangible Book Value (3/31/2021)• 138% (1) Pay to Trade Ratio• 70% Transaction Value / LTM Earnings• 15.3x (2) Transaction Value / 2022E Earnings • 18.5x (2) (3) Transaction Value / 2022E Earnings + Synergies • 10.6x (4) Pro Forma with MFNC Standalone (2) Estimated 2022E EPS Accretion • 3.1%• 9.5% (75% Cost Savings Phase-In) (2) Estimated 2022E EPS Accretion • 5.4%• 12.7% (100% Cost Savings Phase-In) TBVPS Accretion / (Dilution)• (1.2%)• (1.9%) Tangible Book Value Earnback• 1.4 years• 1.4 years TCE / TA Ratio (estimated at close)• 8.2%• 8.5% CET1 Ratio (estimated at close) • 10.9%• 11.2% Internal Rate of Return• 20% + (1) Ratio of tangible book value multiple paid to Nicolet's tangible book value multiple as of June 21, 2021, presented pro forma for Nicolet's announced acquisition of Mackinac Financial Corporation (2) Based on mean consensus estimates 12 (3) Assumes 100% phase-in of cost savings (4) Nicolet and County combined; excludes impact of MFNC

Experienced & Seasoned M&A Leader in the Upper Midwest $7.5 B $4.6 B $3.6 B $3.1 B $2.9 B $2.3 B $1.2 B $1.2 B $1.2 B $0.7 B 2012 2013 2014 2015 2016 2017 2018 2019 2020 Pro Forma 2017 2016 2013 2019 2020 First Menasha Baylake Corp Mid-Wisconsin Financial Services Choice Bancorp Advantage Bancshares Bank of Wausau (FDIC assisted) Community 2021 Bancshares Mackinac Financial County Bancorp 13 AssetsExperienced & Seasoned M&A Leader in the Upper Midwest $7.5 B $4.6 B $3.6 B $3.1 B $2.9 B $2.3 B $1.2 B $1.2 B $1.2 B $0.7 B 2012 2013 2014 2015 2016 2017 2018 2019 2020 Pro Forma 2017 2016 2013 2019 2020 First Menasha Baylake Corp Mid-Wisconsin Financial Services Choice Bancorp Advantage Bancshares Bank of Wausau (FDIC assisted) Community 2021 Bancshares Mackinac Financial County Bancorp 13 Assets

Summary Transaction Highlights County is the ideal partner, accelerating the ability to deploy excess liquidity into higher- growth lending opportunities, in addition to substantially improving County’s funding costs Attractive financial returns with solid EPS accretion, minimal tangible book value dilution and short TBV earnback (pro forma with Mackinac, and on a stand alone basis) Complimentary entrepreneurial cultures with founder mentalities Further diversifies Nicolet’s loan portfolio and revenue mix by acquiring leading agricultural lender, creating the “lead local” community bank that reflects its local economy ~$7.5 billion in total assets, creating the predominant community banking and agricultural \ lending franchise in the Upper Midwest Mackinac transaction remains on course to close in early September 14Summary Transaction Highlights County is the ideal partner, accelerating the ability to deploy excess liquidity into higher- growth lending opportunities, in addition to substantially improving County’s funding costs Attractive financial returns with solid EPS accretion, minimal tangible book value dilution and short TBV earnback (pro forma with Mackinac, and on a stand alone basis) Complimentary entrepreneurial cultures with founder mentalities Further diversifies Nicolet’s loan portfolio and revenue mix by acquiring leading agricultural lender, creating the “lead local” community bank that reflects its local economy ~$7.5 billion in total assets, creating the predominant community banking and agricultural \ lending franchise in the Upper Midwest Mackinac transaction remains on course to close in early September 14

Mike Daniels President & CEO (920) 430-7318 mdaniels@nicoletbank.com Bob Atwell Executive Chairman (920) 430-7317 batwell@nicoletbank.com Phil Moore Chief Financial Officer (920) 617-8159 pmoore@nicoletbank.com Eric Radzak Corporate Development Officer / Investor Relations (920) 617-4540 eradzak@nicoletbank.comMike Daniels President & CEO (920) 430-7318 mdaniels@nicoletbank.com Bob Atwell Executive Chairman (920) 430-7317 batwell@nicoletbank.com Phil Moore Chief Financial Officer (920) 617-8159 pmoore@nicoletbank.com Eric Radzak Corporate Development Officer / Investor Relations (920) 617-4540 eradzak@nicoletbank.com