The person shall maintain records which permit specific identification of each piece of section 179 property and reflect how and from whom such property was acquired and when such property was placed in service. However, for this purpose a partner (or an S corporation shareholder) treats partnership (or S corporation) section 179 property for which section 179 expenses are allocated from a partnership (or an S corporation) as one item of section 179 property. The election to claim a section 179 expense deduction under this section, with respect to any property, is irrevocable and will be binding on the taxpayer with respect to such property for the taxable year for which the election is made and for all subsequent taxable years, unless the Commissioner consents to the revocation of the election. Similarly, the selection of section 179 property by the taxpayer to be subject to the expense deduction and apportionment scheme must be adhered to in computing the taxpayer's taxable income for the taxable year for which the election is made and for all subsequent taxable years, unless consent to change is given by the Commissioner.
26 C.F.R. §1.179-5