There IS an actual form for making this election. It is Form 3115.
DCN64 (DCN stands for “Designated automatic accounting method change") is used to make this election.
Form 3115 can be found at:
<a rel="nofollow" target="_blank" href="
https://www.irs.gov/pub/irs-pdf/i3115.pdf">https://www.irs.gov/pub/irs-pdf/i3115.pdf</a>
