@TaxGuyBill From 2021 pub 946 An election (or any specification made in the election) to take a section 179 deduction for 2021 can be revoked without IRS approval by filing an amended return. The amended return must be filed within the time prescribed by law.  Pub 946 says the same thing the regs said. I read that as meaning you must file Form 1040-X within 3 years after the date you timely filed your original return or within 2 years after the date you paid the tax, whichever is later.