Title II — TAX ON INCOME Finance, upon recommendation of the Commissioner, the taxpayer and the Commissioner have entered into an agreement in writing specifically dealing with the useful life and rate of depreciation of any property, the rate so agreed upon shall be binding on both the taxpayer and the National Government in the absence of facts and circumstances not taken into consideration during the adoption of such agreement. The responsibility of establishing the existence of such facts and circumstances shall rest with the party initiating the modification. Any change in the agreed rate and useful life of the depreciable property as specified in the agreement shall not be effective for taxable years prior to the taxable year in which notice in writing by certified mail or registered mail is served by the party initiating such change to the other party to the agreement: Provided, however, That where the taxpayer has adopted such useful life and depreciation rate for any depreciable asset and claimed the depreciation expenses as deduction from his gross income, without any written objection on the part of the Commissioner or his duly authorized representative, the aforesaid useful life and depreciation rate so adopted by the taxpayer for the aforesaid depreciable asset shall be considered binding for purposes of this Subsection. (4) Depreciation of Properties Used in Petroleum Operations. — An allowance for depreciation in respect of all properties directly related to production of petroleum initially placed in service in a taxable year shall be allowed under the straight-line or declining-balance method of depreciation at the option of the service contractor. However, if the service contractor initially elects the decliningbalance method, it may at any subsequent date, shift to the straightline method. The useful life of properties used in or related to production of petroleum shall be ten (10) years or such shorter life as may be permitted by the Commissioner. Properties not used directly in the production of petroleum shall be depreciated under the straight-line method on the basis of an estimated useful life of five (5) years. (5) Depreciation of Properties Used in Mining Operations. — An allowance for depreciation in respect of all properties used in mining operations other than petroleum operations, shall be computed as follows: (a) At the normal rate of depreciation if the expected life is ten (10) years or less; or National Internal Revenue Code of 1997 (as amended by the TRAIN Law, RAs 11256, 11346 and 11467) 53