1 EXHIBIT 8.1 [Letterhead of Arnold & Porter] [Form of Tax Opinion] July 28, 2000 M&T Bank Corporation One M&T Plaza Buffalo, New York 14203 Ladies and Gentlemen: You have requested our opinion as to certain federal income tax consequences of the proposed merger (the "Merger") of Keystone Financial, Inc. ("Keystone") with and into Olympia Financial Corp. ("Olympia"), a wholly owned subsidiary of M&T Bank Corporation ("M&T"). In preparing our opinion, and with your permission, we have assumed (1) that the Merger will be consummated in accordance with the terms, conditions and other provisions of the Agreement and Plan of Reorganization by and among Keystone, M&T and Olympia, dated as of May 16, 2000 (the "Reorganization Agreement"), the Agreement and Plan of Merger by and between Keystone and Olympia and joined in by M&T as of May 16, 2000 (the "Plan of Merger"), and the Option Agreement,(1) and (2) that all of the factual information, descriptions, representations and assumptions set forth or referred to (a) in this letter (an advance copy of which has been provided to you), (b) in the Reorganization Agreement, the Plan of Merger and the Option Agreement (the "Agreements"), (c) in letters to us from M&T and Olympia dated July 28, 2000, and from Keystone dated July 28, 2000 (the "Letters"), and (d) in the Prospectus/Proxy Statement prepared in connection with the Merger, are accurate and complete and will be accurate and complete as of the effective time of the Merger ("Effective Time"). We have not independently verified any factual matters relating to the Merger in connection with or apart from our preparation of this opinion. Accordingly, our opinion does not take into account any matters not set forth herein which might have been disclosed by independent verification. - ------------------- (1) Terms not otherwise defined in this letter shall have the meanings assigned to them in the Reorganization Agreement. 2 M&T Bank Corporation July 28, 2000 Page 2 OPINION Based on the foregoing, and subject to the qualifications and other matters set forth herein, it is our opinion that for federal income tax purposes: 1. The Merger will be treated as a reorganization within the meaning of Section 368(a) of the Internal Revenue Code of 1986, as amended (the "Code"); 2. Keystone, M&T and Olympia will each be a party to the reorganization within the meaning of Section 368(b) of the Code; 3. No gain or loss will be recognized by M&T, Olympia or Keystone as a result of the merger (except for amounts resulting from any required change in accounting methods or any income or deferred gain recognized under the relevant consolidated return regulations); 4. Keystone shareholders who receive only M&T common stock for all of their shares of Keystone stock will not recognize any gain or loss with respect to shares of M&T stock received (except with respect to cash received instead of a fractional share interest in M&T common stock); 5. Each Keystone shareholder who receives M&T common stock and cash (other than cash instead of a fractional share interest in M&T common stock) in exchange for the shareholder's shares of Keystone common stock will recognize the gain, if any, realized by the shareholder, in an amount not in excess of the amount of cash received, but will not recognize any loss on the exchange; 6. Each Keystone shareholder's aggregate tax basis in any shares of M&T common stock received in the transaction (including fractional shares deemed received and redeemed) will be the same as the aggregate tax basis of the shares of Keystone common stock the Keystone shareholder surrendered in exchange therefor, decreased by the amount of any cash received by the shareholder and increased by the amount of income or gain recognized by the shareholder in the exchange; and 7. Each Keystone shareholder's holding period in any shares of M&T common stock received in the transaction (including any fractional shares deemed 3 M&T Bank Corporation July 28, 2000 Page 3 received and redeemed) will, in each instance, include the period during which the shares of Keystone common stock surrendered in exchange therefor were held. This opinion may not apply to a Keystone shareholder that is subject to special treatment under the Code, such as a shareholder that is a financial institution, an insurance company, a dealer in securities or foreign currencies, a trader in securities, a tax-exempt organization, a person who holds shares of Keystone common stock in an individual retirement account (IRA), 401(k) plan or similar tax-favored account, a person who acquired shares of Keystone common stock pursuant to the exercise of an employee stock option or otherwise as compensation or a person who holds shares of Keystone common stock as part of a hedge, straddle, conversion or constructive sale transaction. Our opinion is limited to the foregoing federal income tax consequences of the Merger, which are the only matters as to which you have requested our opinion, and you must judge whether the matters addressed herein are sufficient for your purposes. We do not address any other federal income tax consequences of the Merger or other matters of federal law and have not considered matters (including state or local tax consequences) arising under the laws of any jurisdiction other than matters of federal law arising under the laws of the United States. Our opinion is based on the understanding that the relevant facts are, and will be as of the Effective Time, as set forth or referred to in this letter. If this understanding is incorrect or incomplete in any respect, our opinion could be affected. Our opinion is also based on the Code, Treasury Regulations, case law, and Internal Revenue Service rulings as they now exist. These authorities are all subject to change and such change may be made with retroactive effect. We can give no assurance that after any such change, our opinion would not be different. Moreover, our opinion is not binding on the Internal Revenue Service or the courts. We undertake no responsibility to update or supplement this opinion. Our opinion is issued to M&T. Only M&T may rely on our opinion, and only with respect to the Merger described herein. We hereby consent to the filing with the Securities and Exchange Commission of this opinion as an exhibit to the Registration Statement on Form S-4 and to the reference to our firm under the heading "THE MERGER -- Certain Federal Income Tax Consequences" in the Prospectus/Proxy Statement contained therein. In giving such 4 M&T Bank Corporation July 28, 2000 Page 4 consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act of 1933. Very truly yours, /s/ Arnold & Porter ARNOLD & PORTER