Thanks Lisa995.
This, from IRS' Publication 544:
Election to postpone gain.
Report your election to postpone reporting your gain, along with all necessary details,
on a statement attached to your return for the tax year in which you realize the gain
.
Replacement property acquired after return filed.
If you buy the replacement property after you file your return reporting your election to postpone reporting the gain, attach a statement to your return
for the year in which you buy the property
. The statement should contain detailed information on the replacement property.
Amended return.
If you elect to postpone reporting gain, you must file an amended return for the year of the gain (individuals file Form 1040X) in either of the following situations:
- You do not buy replacement property within the replacement period. On your amended return, you must report the gain and pay any additional tax due.
- The replacement property you buy costs less than the amount realized for the condemned property (minus the gain you excluded from income if the property was your main home). On your amended return, you must report the part of the gain you cannot postpone reporting and pay any additional tax due.
Here is the full text of Publication 544, Sales and Other Dispositions of Assets. Section 1033 begins on page 10:
