There is no form or process for TTS. TTS is based on facts and circumstances as seen in the eyes of the IRS. A taxpayer "claims" to be TTS. No checkbox, no form, no specific process. Greens "rules" are derived from court case law, due to the no checkbox, form, or process being available. Written footnotes on tax filings and/or corporate minutes may be useful or even required, based on business structure. In many, but not all cases, Form 3115 is necessary for election of the MTM change of accounting. As you point out, TTS allows the option of electing MTM. MTM change of accounting and all the associated MTM accounting benefits (wash sales, business loss limits, NOL carry, etc, etc.) are not valid without TTS.