Rev. Proc. 2024-28, page 326.

Subject to certain requirements, this Revenue Procedure generally permits taxpayers to rely on any reasonable allocation of units unattached basis to a digital asset wallet or account that holds the same number of remaining digital asset units based on the taxpayer’s records of such unattached basis and remaining units. The allocation must be a reasonable allocation as defined in section 5.02 of this Revenue Procedure and must be made as of January 1, 2025. However, the taxpayer may identify the method of allocation and may comply with the requirements set forth in section 4.02 of this Revenue Procedure at a later date to the extent permitted by section 5.02(4) or 5.02(5) of this Revenue Procedure.