For taxpayers who have filed their 2024 returns and are eligible small businesses as far as the R&E expense treatment changes, under this Rev Proc, you MAY file a superseding return before 9/15 (or 10/15 for C-Corps) to make the expense adjustment— regardless of whether you filed for an extension prior to 3/15 (4/15). It is automatic extension for this purpose but requires a statement of treatment with the superseding return.