this is from 26 CRF 1.179-5. Here is the link: https://www.law.cornell.edu/cfr/text/26/1.179-5

(a) Election. A separate election must be made for each taxable year in which a section 179 expense deduction is claimed with respect to section 179 property. The election under section 179 and § 1.179-1 to claim a section 179 expense deduction for section 179 property shall be made on the taxpayer's first income tax return for the taxable year to which the election applies (whether or not the return is timely) or on an amended return filed within the time prescribed by law (including extensions) for filing the return for such taxable year. The election shall be made by showing as a separate item on the taxpayer's income tax return the following items: