For reference, here are excerpts from IRS publications relevant to OZ deferrals. IRS uses the term "eligible gain", but I have not been able to find a definition of what is eligible. I cannot give tax advise, but I would personally interpret this as anything which appears on my Form 8949.
From IRS:
"Use Form 8949 to report the sale or exchange of a capital asset (defined later) not reported on another form or schedule and to report the income deferral or exclusion of capital gains. See the Instructions for Form 8949."
On 8949, it's buried in 1(f) and 1(g):
"1 (a) Description of property (Example: 100 sh. XYZ Co.) (b) Date acquired (Mo., day, yr.) (c) Date sold or disposed of (Mo., day, yr.) (d) Proceeds (sales price) (see instructions) (e) Cost or other basis. See the Note below and see Column (e) in the separate instructions Adjustment, if any, to gain or loss. If you enter an amount in column (g), enter a code in column (f). See the separate instructions. (f) Code(s) from instructions (g) Amount of adjustment (h) Gain or (loss). Subtract column (e) from column (d) and combine the result with column (g) "
Then, per the 8949 instructions, you use code Z:
You are electing to postpone all or part of your gain under the rules explained in the Schedule D instructions for investments in QO Fund(s)
Z
See How To Report an Election To Defer Tax on Eligible Gain Invested in a QO Fund, later.
And,How To Report an Election To Defer Tax on Eligible Gain Invested in a QO Fund
If you elect to defer tax on an eligible gain by investing in a QO Fund, report the eligible gain on the form and in the manner otherwise instructed. For example, individual taxpayers would report gain from the sale of stock on Form 8949 and Schedule D (Form 1040). If the gain is reported on Form 8949, do not make any adjustments for the deferral in column (g).
Report the deferral of the eligible gain on its own row of Form 8949 in Part I with box C checked or Part II with box F checked (depending on whether the gain being deferred is short-term or long-term). If you made multiple investments in different QO Funds or in the same QO Fund on different dates, use a separate row for each investment. If you invested eligible gains of the same character (but from different transactions) on the same date into the same QO Fund, you can group those investments on the same row. In column (a), enter only the EIN of the QO Fund into which you invested. In column (b), enter the date you invested in the QO Fund. Leave columns (c), (d), and (e) blank. Enter code "Z" in column (f) and the amount of the deferred gain as a negative number (in parentheses) in column (g).
Your investment in a QO Fund can be used to defer only long-term gain, only short-term gain, or a combination of both short-term and long-term gain. You do not need to trace or allocate the funds invested in a QO Fund to the specific gain being deferred, but the investment in the QO Fund must have occurred within the 180-day period beginning on the date the deferred gain was realized. If you realized both short-term and long-term gains during the 180-day period you can choose how much of each gain to defer by reporting the deferral in Part I or Part II, as applicable. The character of the eligible gain will survive the investment in the QO Fund. When you recognize the eligible gain (either when you sell or exchange your investment in the QO Fund or December 31, 2026, whichever is earlier), the gain you recognize will be the same character as the gain you deferred.
