QUESTIONS AND ANSWERS ABOUT THE MERGER AND THE SPECIAL MEETINGS

The following questions and answers are intended to address briefly some commonly asked questions regarding the merger and the special meetings. These questions and answers may not address all questions that may be important to you as a stockholder. To better understand these matters, and for a description of the legal terms governing the merger, you should carefully read this entire joint proxy statement/prospectus, including the annexes, as well as the documents that have been incorporated by reference in this joint proxy statement/prospectus.

We are delivering this joint proxy statement/prospectus to you as both a joint proxy statement of NBT and Alliance and a prospectus of NBT. It is a joint proxy statement because the boards of directors of both NBT and Alliance are soliciting proxies from their respective stockholders to vote on the adoption and approval of the merger agreement at their respective special meetings of stockholders. Your proxy will be used at your respective special meeting or at any adjournment or postponement of that special meeting. It is also a prospectus because NBT will issue NBT common stock to Alliance shareholders as consideration in the merger, and this prospectus contains information about that common stock.

The value of the stock consideration is dependent upon the value of NBT common stock and therefore will fluctuate with the market price of NBT common stock. Accordingly, any change in the price of NBT common stock prior to the merger will affect the market value of the stock consideration that Alliance shareholders will receive as a result of the merger.

NBT Stockholders. NBT stockholders will continue to hold their existing shares, which will not change as a result of the merger.

NBT Stockholders: All holders of NBT common stock who held shares at the close of business on January 14, 2013, which is the record date for the special meeting of NBT stockholders, are entitled to receive notice of and to vote at the NBT special meeting. Each holder of NBT common stock is entitled to one vote for each share of NBT common stock owned as of the record date.

You should send any notice of revocation to the appropriate company at:

If you have instructed a bank, broker or other nominee to vote your shares, you must follow the directions you receive from your bank, broker or other nominee to change your voting instructions.

Q: What happens if I sell my shares after the record date but before the special meeting?

SUMMARY

This summary highlights selected information from this joint proxy statement/prospectus. It does not contain all of the information that may be important to you. We urge you to read carefully the entire document and the other documents to which this joint proxy statement/prospectus refers in order to fully understand the merger and the related transactions. See “Where You Can Find More Information” beginning on page 166. Each item in this summary refers to the page of this joint proxy statement/prospectus on which that subject is discussed in more detail.

The Companies (Page 35)

NBT Bancorp Inc.

NBT is a registered financial holding company incorporated in Delaware in 1986, with its principal headquarters located in Norwich, New York. NBT is the parent holding company of NBT Bank, N.A., NBT Financial Services, Inc. (which operates EPIC Advisors, Inc.), and NBT Holdings, Inc. (which operates Mang Insurance Agency, LLC), NBT Capital Trust I, NBT Statutory Trust I and NBT Statutory Trust II.

NBT Bank is a national bank with 137 locations, including 95 NBT Bank offices located in upstate New York, northwestern Vermont and western Massachusetts, 35 Pennstar Bank offices located in northeastern Pennsylvania, and 5 Hampshire First Bank offices located in southern New Hampshire. NBT Bank provides its retail consumers and business customers with banking services including residential and commercial real estate loans, commercial business loans, consumer loans, as well as retail and commercial deposit products, various trust services, as well as investment, pension, estate planning and employee benefit administrative services.

At September 30, 2012, NBT had $6.0 billion in assets, $4.8 billion in deposits, and $577.0 million of stockholders’ equity.

NBT’s principal executive offices are located at 52 South Broad Street, Norwich, New York 13815, its phone number is (607) 337-2265 and its website is www.nbtbancorp.com. Information that is included in this website does not constitute part of this joint proxy statement/prospectus.

Alliance Financial Corporation

Alliance is a New York corporation and a registered financial holding company formed on November 25, 1998, as a result of the merger of Cortland First Financial Corporation and Oneida Valley Bancshares, Inc., which were incorporated on May 30, 1986 and October 31, 1984, respectively. Alliance is the holding company of Alliance Bank, which was formed as the result of the merger of First National Bank of Cortland and Oneida Valley National Bank in 1999.

Alliance Bank provides financial services from 29 retail branches and customer service facilities in the New York counties of Cortland, Madison, Oneida, Onondaga and Oswego, and from a Trust Administration Center in Buffalo, New York. Primary services include commercial, retail and municipal banking, consumer finance, mortgage financing and servicing, and trust and investment management services. Alliance Bank has a substantially wholly owned subsidiary, Alliance Preferred Funding Corp., which is engaged in residential real estate activity, and a wholly owned subsidiary, Alliance Leasing, Inc., which is engaged in commercial leasing activity in over 30 states.

At September 30, 2012, Alliance had $1.4 billion in assets, $1.1 billion in deposits, and $148.4 million of shareholders’ equity.

Alliance’s principal executive offices are located on the 18th Floor, 120 Madison Street, Syracuse, New York 13202. Alliance’s telephone number is (315) 475-2100 and its website is www.alliancefinancialcorporation.com. Information that is included in this website does not constitute part of this joint proxy statement/prospectus.

The Special Meeting of Shareholders of Alliance

Date, Time and Place of the Special Meeting (Page 36)

Alliance will hold its special meeting of shareholders at Alliance Financial Corporation, 120 Madison Street, 18^th Floor, Syracuse, New York 13202 on March 7, 2013, at 10:00 a.m., local time.

Purpose of the Special Meeting (Page 36)

At the special meeting you will be asked to vote upon a proposal to adopt the merger agreement, a proposal to approve, on an advisory (non-binding) basis, the golden parachute compensation payable to the named executive officers of Alliance in connection with the merger and, if necessary, a proposal to approve one or more adjournments of the special meeting.

Recommendation of Alliance Board of Directors (Page 36)

The Alliance board of directors unanimously recommends that you vote “FOR” adoption of the merger agreement, “FOR” approval, on an advisory (non-binding) basis, of the golden parachute compensation payable to the named executive officers of Alliance in connection with the merger, and “FOR” approval of the proposal to adjourn the special meeting.

Record Date; Outstanding Shares; Shares Entitled to Vote (Page 36)

Only holders of record of Alliance common stock at the close of business on the record date of January 23, 2013, are entitled to notice of and to vote at the special meeting. As of the record date, there were 4,782,185 shares of Alliance common stock outstanding, held of record by approximately 843 shareholders.

Quorum; Vote Required (Page 36)

A quorum of Alliance shareholders is necessary to hold a valid meeting. If the holders of at least a majority of the total number of the outstanding shares of Alliance common stock entitled to vote are represented in person or by proxy at the special meeting, a quorum will exist. Alliance will include proxies marked as abstentions and broker non-votes in determining the presence of a quorum at the special meeting.

The affirmative vote of the holders of at least two-thirds of the outstanding shares of Alliance common stock is required to adopt the merger agreement. The affirmative vote of the holders of at least a majority of votes cast is required to approve, on an advisory (non-binding) basis, the golden parachute compensation payable to the named executive officers of Alliance in connection with the merger, and the proposal to adjourn the special meeting.

Share Ownership of Management; Voting Agreement (Page 37)

As of the record date, the directors and executive officers of Alliance and their affiliates collectively owned 475,617 shares of Alliance common stock, or approximately 9.95% of Alliance’s outstanding shares. Alliance currently expects that each of its directors and executive officers and their affiliates will vote their shares of Alliance common stock “FOR” adoption of the merger agreement and the other proposals described in the notice for the special meeting, although, except for Alliance’s Chairman, Chief Executive Officer and President, Jack H. Webb, none of them has entered into an agreement requiring them to do so.

Mr. Webb has entered into a voting agreement with NBT, which requires Mr. Webb to vote all of the shares of Alliance common stock beneficially owned by him in favor of adoption of the merger agreement. As of the record date, Mr. Webb held 56,617 shares of Alliance common stock, which represented approximately 1.18% of the outstanding shares of Alliance common stock as of the record date. Mr. Webb was not paid any additional consideration in connection with the execution of the voting agreement. In addition, NBT holds 39,693 shares of Alliance common stock, which represented approximately 0.8% of the outstanding shares of Alliance common stock as of the record date.

The Special Meeting of Stockholders of NBT

Date, Time and Place of the Special Meeting (Page 40)

NBT will hold its special meeting of stockholders at the Binghamton Riverwalk Hotel & Conference Center, 225 Water Street, Binghamton, New York 13901 on March 5, 2013, at 10:00 a.m., local time.

Purpose of the Special Meeting (Page 40)

At the special meeting you will be asked to vote upon a proposal to adopt and approve the merger agreement and, if necessary, a proposal to approve one or more adjournments of the special meeting.

Recommendation of NBT Board of Directors (Page 40)

The NBT board of directors unanimously recommends that you vote “FOR” adoption and approval of the merger agreement and “FOR” approval of the proposal to adjourn the special meeting.

Record Date; Outstanding Shares; Shares Entitled to Vote (Page 40)

Only holders of record of NBT common stock at the close of business on the record date of January 14, 2013, are entitled to notice of and to vote at the special meeting. As of the record date, there were 33,762,092 shares of NBT common stock outstanding, held of record by approximately 6,598 stockholders.

Quorum; Vote Required (Page 40)

A quorum of NBT stockholders is necessary to hold a valid meeting. If the holders of at least a majority of the total number of the outstanding shares of NBT common stock entitled to vote are represented in person or by proxy at the special meeting, a quorum will exist. NBT will include proxies marked as abstentions and broker non-votes in determining the presence of a quorum at the special meeting.

The affirmative vote of the holders of at least a majority of the outstanding shares of NBT common stock is required to adopt and approve the merger agreement. The affirmative vote of the holders of at least a majority of the shares present and entitled to vote at the special meeting is required to approve the proposal to adjourn the special meeting.

Share Ownership of Management (Page 41)

As of the record date, the directors and executive officers of NBT and their affiliates collectively owned 1,140,693 shares of NBT common stock, or approximately 3.38% of NBT’s outstanding shares. NBT currently expects that each of its directors and executive officers and their affiliates will vote their shares of NBT common stock “FOR” adoption and approval of the merger agreement, although none of them has entered into an agreement requiring them to do so.

The Merger and the Merger Agreement

The proposed merger is of Alliance with and into NBT, with NBT as the surviving corporation in the merger. The merger agreement is attached to this joint proxy statement/prospectus as Annex A. Please carefully read the merger agreement as it is the legal document that governs the merger.

Structure of the Merger (Page 84)

Subject to the terms and conditions of the merger agreement, and in accordance with the Delaware General Corporation Law and the New York Business Corporation Law, at the completion of the merger, Alliance will merge with and into NBT. NBT will be the surviving corporation in the merger and will continue its corporate existence under the laws of the State of Delaware. Upon completion of the merger, the separate corporate existence of Alliance will terminate.

Consideration to be Received in the Merger (Page 85)

Upon completion of the merger, each outstanding share of Alliance common stock (other than any stock held by Alliance or NBT, which will be cancelled) will be converted into the right to receive 2.1779 shares of NBT common stock (together with the associated stock purchase rights which are attached to, and trade with, shares of NBT common stock).

No fractional shares of NBT common stock will be issued to any holder of Alliance common stock upon completion of the merger. For each fractional share that would otherwise be issued, NBT will pay each shareholder cash (without interest) in an amount equal to the fractional share interest to which such shareholder would otherwise be entitled multiplied by the average of the daily closing prices of NBT common stock during the regular session of NBT common stock on NASDAQ for the five consecutive trading days ending on the third business day immediately prior to the closing date, rounded to the nearest whole cent.

Treatment of Stock-Based Awards (Page 85)

At the effective time of the merger, all of the then outstanding Alliance restricted stock awards will fully vest in accordance with their existing terms, and all of the related shares will be converted in the merger into the right to receive the same merger consideration for which other outstanding shares of Alliance common stock will be exchanged in the merger.

Treatment of Alliance’s Deferred Compensation Plans (Page 86)

Without any action of any participant in any Alliance stock-based deferred compensation plan, all amounts held in participant accounts and denominated in Alliance common stock will be converted in accordance with the existing terms of such plans into the number of shares of NBT common stock that is equal to the number of shares of Alliance common stock immediately prior to the effective time multiplied by 2.1779.

Opinion of Keefe, Bruyette & Woods, Inc., Financial Advisor to Alliance (Page 53)

On October 7, 2012, Keefe, Bruyette & Woods, Inc., or KBW, rendered to the Alliance board of directors its oral opinion, subsequently confirmed in writing that, as of such date, the consideration to be received in the merger was fair to Alliance shareholders from a financial point of view. The full text of KBW’s written opinion, which sets forth the assumptions made, matters considered and qualifications and limitations on the review undertaken in connection with the opinion, is attached to this document as Annex B. Alliance shareholders are urged to read the opinion in its entirety. KBW’s opinion speaks only as of the date of the opinion. The opinion is directed to the Alliance board of directors and addresses only the fairness, from a financial point of view, of the exchange ratio to the holders of Alliance common stock. It does not address the underlying business decision to proceed with the merger and does not constitute a recommendation to any Alliance shareholder as to how the shareholder should vote at the Alliance special meeting on the merger agreement or any related matter.

Opinion of Ambassador Financial Group, Financial Advisor to NBT (Page 70)

On October 7, 2012, Ambassador Financial Group, or AFG, rendered to the NBT board its oral opinion, subsequently confirmed in writing that, as of such date, the consideration to be paid in the merger was fair to NBT stockholders from a financial point of view. The full text of AFG’s written opinion, which sets forth the assumptions made, matters considered and qualifications and limitations on the review undertaken in connection with the opinion, is attached to this document as Annex C. NBT stockholders are urged to read the opinion in its entirety. AFG’s written opinion is addressed to the board of directors of NBT and is directed only to the fairness of the merger consideration to NBT stockholders from a financial point of view. The written opinion does not address the underlying business decision of NBT to engage in the merger or any other aspect of the merger and is not a recommendation to any NBT stockholder as to how such stockholder should vote at the special meeting with respect to the merger agreement or any other matter.

Interests of Alliance’s Directors and Executive Officers in the Merger (Page 64)

Alliance executive officers and directors have financial interests in the merger that are in addition to, or different from, the interests of Alliance shareholders generally. These interests include certain payments and benefits that may be provided to directors and executive officers of Alliance upon completion of the merger, including acceleration of restricted stock awards and payment of discretionary bonuses, or upon termination of their employment under specified circumstances at the time of or following the merger, including cash severance and continued health insurance benefits. Additionally, NBT entered into an agreement with Jack H. Webb regarding his continuing role with the combined company following the merger. The Alliance board of directors was aware of those interests and considered them, among other matters, when it approved the merger agreement.

NBT’s and NBT Bank’s Board of Directors After the Merger (Page 78)

Immediately following the effective time of the merger, NBT has agreed that it will designate Jack H. Webb, the current Chairman, Chief Executive Officer and President of Alliance, and two other Alliance directors to serve on the NBT board of directors. The designees shall also be appointed to the board of directors of NBT Bank effective immediately following the effective time of the bank merger.

Bank Merger (Page 78)

The merger agreement provides that as soon as practicable after the consummation of the merger, Alliance Bank shall be merged with and into NBT Bank with NBT Bank surviving.

No Solicitation of Alternative Transactions (Page 91)

The merger agreement restricts Alliance’s ability to solicit or engage in discussions or negotiations with a third party regarding a proposal to acquire a significant interest in Alliance. However, if Alliance receives a bona fide unsolicited written acquisition proposal from a third party that is, or is reasonably likely to be, more favorable to Alliance shareholders than the terms of the merger agreement, Alliance may furnish nonpublic information to that third party and engage in negotiations regarding an acquisition proposal with that third party, subject to specified conditions in the merger agreement. In addition, the Alliance board of directors may not:

However, the Alliance board of directors may modify, qualify, withhold or withdraw its recommendation of the merger agreement if it determines in good faith, after consultation with counsel and a financial advisor, that an acquisition proposal is a superior proposal and, after consultation with counsel, that it is required to take such action to comply with its fiduciary duties to shareholders under applicable law. In that event, Alliance must provide NBT with notice of such determination and cooperate and negotiate in good faith with NBT to adjust or modify the terms and conditions of the merger agreement.

Conditions to Completion of the Merger (Page 96)

As more fully described in this joint proxy statement/prospectus and the merger agreement, the completion of the merger depends on a number of conditions being satisfied or waived, including:

Termination of the Merger Agreement (Page 97)

NBT and Alliance can mutually agree to terminate the merger agreement before the merger has been completed, and either company can terminate the merger agreement if:

In addition, NBT may terminate the merger agreement if:

In addition, Alliance has the right to terminate the merger agreement if the average closing price of NBT common stock for a specified period prior to closing is less than $17.74 and NBT common stock underperforms a specified peer-group index by more than 20%. However, NBT will have the option to increase the amount of NBT common stock to be provided to Alliance shareholders, in which case no termination will occur.

Termination Fee (Page 99)

Alliance has agreed to pay to NBT a termination fee of approximately $9.3 million if:

Waiver or Amendment of Merger Agreement Provisions (Page 100)

At any time prior to the completion of the merger, a provision of the merger agreement may be waived by the party intended to benefit by the provision, or may be amended or modified by a written action taken or authorized by the parties’ respective boards of directors. However, after the approval of the merger agreement by the Alliance shareholders, no amendment will be made which by law requires further approval by Alliance shareholders without such further approval.

Material U.S. Federal Income Tax Consequences of the Merger (Page 78)

The merger is intended to qualify for U.S. federal income tax purposes as a “reorganization” within the meaning of Section 368(a) of the Code. Accordingly, Alliance shareholders generally will not recognize any gain or loss on the conversion of shares of Alliance common stock solely into shares of NBT common stock. However, an Alliance shareholder generally will be subject to tax on cash received in lieu of any fractional share of NBT common stock that an Alliance shareholder would otherwise be entitled to receive.

Regulatory Approvals Required for the Merger (Page 80)

To complete the merger, NBT and Alliance need the prior approval of the Board of Governors of the Federal Reserve Board, or FRB. The United States Department of Justice is able to provide input into the approval process of federal banking agencies to challenge the approval on antitrust grounds. The FRB approved NBT’s request to waive the filing requirements of the Bank Holding Company Act of 1956, as amended, or the BHCA, on January 14, 2013. In addition, the Office of the Comptroller of the Currency, or OCC, approved the merger of Alliance Bank, N.A. into NBT Bank, N.A. on December 21, 2012.

Accounting Treatment of the Merger (Page 81)

The merger will be accounted for using the purchase method of accounting with NBT treated as the acquiror. Under this method of accounting, Alliance’s assets and liabilities will be recorded by NBT at their respective fair values as of the closing date of the merger and added to those of NBT. Any excess of purchase price over the net fair values of Alliance’s assets and liabilities will be recorded as goodwill. Any excess of the fair value of Alliance’s net assets over the purchase price will be recognized in earnings by NBT on the closing date of the merger.

Appraisal Rights (Page 81)

Under the New York General Corporation Law, Alliance shareholders will not have appraisal rights in connection with the merger.

Listing of NBT Common Stock to be Issued in the Merger (Page 81)

NBT’s common stock is quoted on the NASDAQ Global Select Market under the trading symbol “NBTB.”

Charitable Commitments (Page 94)

For a period of three years following the effective time, NBT will continue Alliance’s charitable giving in the region currently served by Alliance at an annual level of at least $300,000.

Differences Between Rights of NBT and Alliance Stockholders (Page 148)

As a result of the merger, holders of Alliance common stock will become holders of NBT common stock. Following the merger, Alliance shareholders will have different rights as stockholders of NBT than as shareholders of Alliance due to the different provisions of the governing documents of NBT and Alliance. For additional information regarding the different rights as stockholders of NBT than as shareholders of Alliance, see “Comparison of Stockholder Rights” beginning on page 148.

RECENT DEVELOPMENTS

NBT’s 2012 Unaudited Financial Results

On January 28, 2013, NBT reported its financial results for the three months and year ended December 31, 2012. NBT reported net income for the year ended December 31, 2012, was $54.6 million, down $3.3 million, or 5.8%, from the year ended December 31, 2011. Net income per diluted share for the year ended December 31, 2012 was $1.62, down from $1.71 per diluted share for the year ended December 31, 2011. Net interest margin (on a fully taxable equivalent or FTE basis) was 3.86% for the year ended December 31, 2012, down 23 basis points from 4.09% for the year ended December 31, 2011. Return on average assets and return on average equity were 0.93% and 9.72%, respectively, for the year ended December 31, 2012, compared with 1.06% and 10.73%, respectively, for the year ended December 31, 2011.

Net income for the three months ended December 31, 2012 was $13.1 million, down $0.6 million, or 4.4%, from the three months ended December 31, 2011. Net income per diluted share for the three months ended December 31, 2012 was $0.39 per share, down from $0.41 per diluted share for the three months ended December 31, 2011. FTE net interest margin was 3.83% for the three months ended December 31, 2012, down 15 basis points from 3.98% for the three months ended December 31, 2011. Annualized return on average assets and return on average equity were 0.86% and 9.01%, respectively, for the three months ended December 31, 2012, compared with 0.97% and 10.09%, respectively, for the three months ended December 31, 2011.

NBT recorded a provision for loan losses of $20.3 million during the year ended December 31, 2012, compared with $20.7 million for the year ended December 31, 2011. Net charge-offs were $22.3 million for the year ended December 31, 2012, up from $20.6 million for the same period in 2011, due primarily to the charge-off of two large commercial loans during the fourth quarter of 2012. Net charge-offs to average loans for the year ended December 31, 2012 was 0.55%, compared to 0.56% for the year ended December 31, 2011.

NBT recorded a provision for loan losses of $6.9 million during the three months ended December 31, 2012, compared with $5.6 million for the three months ended December 31, 2011. Net charge-offs were $8.3 million for the three months ended December 31, 2012 and $5.6 million for the three months ended December 31, 2011.

Past due loans as a percentage of total loans was 0.71% at December 31, 2012, down from 0.89% at December 31, 2011. Nonperforming loans to total loans improved to 0.98% at December 31, 2012 as compared with 1.09% at December 31, 2011.

The allowance for loan losses totaled $69.3 million at December 31, 2012, compared to $71.3 million at December 31, 2011. The allowance for loan losses as a percentage of loans was 1.62% at December 31, 2012, compared to 1.66% at September 30, 2012, 1.70% at June 30, 2012, 1.87% at March 31, 2012, and 1.88% at December 31, 2011. The reduction of the allowance throughout the year was due primarily to the improvement in key asset quality indicators, as well as improvement in certain economic indicators.

Net interest income was up to $204.2 million for the year ended December 31, 2012, compared with $200.3 million for the year ended December 31, 2011. Net interest income was up to $52.5 million for the three months ended December 31, 2012, compared with $50.5 million for the three months ended December 31, 2011.

Noninterest income for the year ended December 31, 2012 was $87.3 million, up 8.7% or $7.0 million, compared with $80.3 million for the same period in 2011. Noninterest income for the three months ended December 31, 2012 was $22.0 million, up 9.1% or $1.8 million, compared with $20.1 million for the same period in 2011. Noninterest expense for the year ended December 31, 2012 was $193.9 million, up $13.2 million or 7.3%, for the same period in 2011. Noninterest expense for the three months ended December 31, 2012 was $48.6 million, up

$1.2 million or 2.5%, for the same period in 2011. NBT incurred approximately $2.6 million in merger related expenses for the year ended December 31, 2012, as compared to $0.8 million for the same period in 2011.

Total assets were $6.0 billion at December 31, 2012, up $443.9 million or 7.9% from December 31, 2011. Loans were $4.3 billion at December 31, 2012, up $477.4 million from December 31, 2011. Total deposits were $4.8 billion at December 31, 2012, up $417.2 million from December 31, 2011. Stockholders’ equity was $582.3 million, representing a total equity-to-total assets ratio of 9.64% at December 31, 2012, compared with $538.1 million or a total equity-to-total assets ratio of 9.61% at December 31, 2011.

Additionally, the NBT board of directors declared a 2013 first-quarter cash dividend of $0.20 per share to be paid on March 15, 2013 to shareholders of record as of March 1, 2013.

Alliance’s 2012 Unaudited Financial Results

On January 28, 2013, Alliance reported its financial results for the three months and year ended December 31, 2012. Alliance reported net income for the three months ended December 31, 2012 of $1.3 million, or $0.28 per diluted common share, compared with $2.8 million, or $0.60 per diluted common share in the year-ago quarter and $2.3 million, or $0.48 per diluted common share in the third quarter of 2012. Net income for the year ended December 31, 2012 was $9.2 million, or $1.92 per diluted share, compared with $13.3 million or $2.80 per diluted share in 2011. Expenses related to the pending acquisition of Alliance by NBT totaled $1.4 million after tax, or $0.31 per share, for the three months ended December 31, 2012, and $2.0 million after tax, or $0.43 per share, for the year ended December 31, 2012.

Total assets were $1.4 billion at December 31, 2012. Loans and leases (net of unearned income) were $928.1 million at the end of 2012, representing growth of $21.7 million from September 30, 2012 and $55.4 million from the end of 2011. The growth in Alliance’s loan portfolio was funded primarily through cash generated from amortization and maturities of investment securities. Deposits totaled $1.1 billion at December 31, 2012 and were relatively unchanged throughout 2012.

Delinquent loans and leases (including non-performing) totaled $12.2 million at December 31, 2012, compared with $10.1 million at September 30, 2012 and $17.0 million at December 31, 2011.

Non-performing assets were $5.5 million or 0.39% of total assets at December 31, 2012, compared with $5.1 million or 0.35% of total assets at September 30, 2012 and $11.7 million or 0.83% of total assets at December 31, 2011.

No provision for credit losses was recorded in the fourth quarter of 2012, compared to provision expense of $800,000 in the year-ago quarter. A negative provision expense of $300,000 was recorded in 2012, compared to provision expense of $1.9 million in 2011. At December 31, 2012, $279,000 or 3% of the allowance for credit losses was considered to be “unallocated” (i.e., not based on either quantitative or qualitative factors, but on broader, non-portfolio specific factors), compared to $698,000 or 8% at September 30, 2012 and $991,000 or 9% at December 31, 2011. The allowance for credit losses was $8.6 million at December 31, 2012 compared with $8.5 million at September 30, 2012 and $10.8 million at December 31, 2011. The ratio of the allowance for credit losses to total loans and leases was 0.93% at December 31, 2012, compared with 0.94% at September 30, 2012 and 1.24% at December 31, 2011. The ratio of the allowance for credit losses to non-performing loans and leases was 178% at December 31, 2012, compared with 207% at September 30, 2012 and 96% at December 31, 2011.

The provision for credit losses as a percentage of net charge-offs was 0% in the fourth quarter compared with 60% in the year-ago quarter. The provision for credit losses as a percentage of net charge-offs was not meaningful in the year-ended December 31, 2012 due to the negative provision that was recorded for the year. The provision for credit losses as a percentage of net charge-offs was 105% in 2011.

Net interest income totaled $9.6 million in the three months ended December 30, 2012, compared with $10.0 million in the year-ago quarter and in the third quarter of 2012. Net interest income for the year ended December 31, 2012 totaled $39.4 million, which was down $3.9 million or 8.9% compared with 2011.

Non-interest income was $5.3 million in the fourth quarter of 2012, compared with $5.1 million in the fourth quarter of 2011 and $4.6 million in the third quarter of 2012. The increase resulted from proceeds from the settlement of a bank-owned life insurance contract during the fourth quarter of 2012. Non-interest income totaled $18.9 million in 2012, compared with $20.0 million in 2011. The $1.2 million decrease from the prior year period resulted largely from $1.3 million in gains on sales of securities recognized in 2011, which were partly offset by a $526,000 increase in gains on the sale of loans during 2012.

Non-interest income (excluding gains on securities sales) accounted for 35.3% of total revenue in the fourth quarter of 2012, compared with 33.6% in the year-ago quarter. Non-interest income (excluding gains on securities sales) accounted for 32.3% of total revenue in 2012, compared with 30.1% in the year-ago period.

Non-interest expenses were $12.8 million in the fourth quarter of 2012, compared with $10.6 million in the year-ago quarter and $11.7 million in the third quarter of 2012. Merger related expenses (pre-tax) of $2.4 million and $991,000 were accrued in the fourth and third quarters of 2012, respectively. Non-interest expenses were $46.4 million in 2012, compared with $43.6 million in 2011. Merger related expenses totaled $3.4 million in 2012, and included $2.7 million for professional fees and $676,000 for employee related accruals for estimated severance payments, retention awards and merger related bonuses.

SELECTED CONSOLIDATED HISTORICAL FINANCIAL DATA OF NBT BANCORP INC.

The following tables set forth selected historical financial and other data of NBT for the periods and at the dates indicated. The information is derived in part from and should be read together with the audited consolidated financial statements and notes thereto of NBT incorporated by reference elsewhere in this joint proxy statement/prospectus. The information at and for the nine months ended September 30, 2012 and 2011 is unaudited. However, in the opinion of management of NBT, all adjustments, consisting of normal recurring adjustments necessary for a fair presentation of the results of operations for the unaudited periods have been made. The selected operating data presented below for the nine months ended September 30, 2012 and 2011 are not necessarily indicative of the results that may be expected for future periods.

SELECTED CONSOLIDATED HISTORICAL FINANCIAL DATA OF

ALLIANCE FINANCIAL CORPORATION

The following tables set forth selected historical financial and other data of Alliance for the periods and at the dates indicated. The information is derived in part from and should be read together with the audited consolidated financial statements and notes thereto of Alliance incorporated by reference elsewhere in this joint proxy statement/prospectus. The information at and for the nine months ended September 30, 2012 and 2011 is unaudited. However, in the opinion of management of Alliance, all adjustments, consisting of normal recurring adjustments necessary for a fair presentation of the results of operations for the unaudited periods, have been made. The selected operating data presented below for the nine months ended September 30, 2012 and 2011 are not necessarily indicative of the results that may be expected for future periods.