26 C.F.R. § 1.167(d)-1
After August 16, 1954, a taxpayer may, for taxable years ending after December 31, 1953, enter into an agreement with respect to the estimated useful life, method and rate of depreciation and treatment of salvage of any property which is subject to the allowance for depreciation. An application for such agreement may be made to the district director for the internal revenue district in which the taxpayer's return is required to be filed. Such application shall be filed in quadruplicate and shall contain in such detail as may be practical the following information:
The agreement must be in writing and must be signed by the taxpayer and by the district director. The agreement must be signed in quadruplicate, and two of the signed copies will be returned to the taxpayer. The agreement shall set forth its effective date, the estimated remaining useful life, the estimated salvage value, and rate and method of depreciation of the property and the facts and circumstances taken into consideration in adoption of the agreement, and shall relate only to depreciation allowances for such property on and after the effective date of the agreement. Such an agreement shall be binding on both parties until such time as facts and circumstances which were not taken into account in making the agreement are shown to exist. The party wishing to modify or change the agreement shall have the responsibility of establishing the existence of such facts and circumstances. Any change in the useful life or rate specified in such agreement shall be effective only prospectively, that is, it shall be effective beginning with the taxable year in which notice of the intention to change, including facts and circumstances warranting the adjustment of useful life and rate, is sent by the party proposing the change to the other party and is sent by registered mail, if such notice is mailed before September 3, 1958, or is sent by certified mail or registered mail, if such notice is mailed after September 2, 1958. A copy of the agreement (and any modification thereof) shall be filed with the taxpayer's return for the first taxable year which is affected by the agreement (or any modification thereof). A signed copy should be retained with the permanent records of the taxpayer. For rules relating to changes in method of depreciation, see § 1.167(e)-1 and section 446 and the regulations thereunder.
26 C.F.R. §1.167(d)-1