The short answer
The identification period is the 45 days after you transfer your relinquished property in which you must identify replacement property in writing; it begins on the transfer date and ends at midnight on the 45th day. It comes from section 1031(a)(3)(A) of the Code and Treasury Regulation section 1.1031(k)-1(b)(2)(i). Property you actually receive within those 45 days counts as identified without any notice.
At a glance
| Length | 45 calendar days, ending at midnight on day 45 |
|---|---|
| Starts | The day the relinquished property is transferred |
| Form | A signed writing sent to a person involved in the exchange |
| Limit | Three properties, or more within the 200% value cap |
Forty-five calendar days, counted from the transfer and ending at midnight
Section 1031(a)(3)(A) treats property as not like-kind if it is not identified on or before the day which is 45 days after you transfer the property relinquished. The regulation turns that into a defined window that begins on the date of transfer and ends at midnight on the 45th day thereafter.
The transfer date is day zero, so day 1 is the next calendar day. The regulation counts every calendar day and says nothing about weekends or holidays; our answer on a 45th day that lands on a weekend or holiday covers that question. If one exchange includes several sales, the period runs from the earliest transfer.
The 45 days are not separate from the 180-day exchange period. Both start on the same day, so identification uses the first quarter of the time you have to close.
The regulation's own example shows how one late day voids an identification
The regulation's examples assume a transfer on May 17, 1991, with the identification period ending July 1, 1991. In Example 1 the taxpayer names property E in a signed document delivered on July 2. Because that was one day late, property E is treated as not like-kind.
A current hypothetical: you close on June 1, 2026. Day 45 is Thursday, July 16, 2026, and your written identification notice must be sent by midnight that day. Any revocation or substitution must also be made in writing by then.
One shortcut is built in. Under paragraph (c)(1), replacement property you receive before the period ends is treated as identified, so closing a replacement inside the 45 days is its own identification.
Where it bites: the list you hold at midnight on day 45 is the list you live with
After day 45 you cannot add, swap or revoke. If every identified property later falls through, there is nothing left you may buy; see what happens when an identified property falls through after day 45.
The count limits apply to everything still on the list when the period ends: three properties of any value, or any number whose total stays within 200% of the value you sold. Exceed both and the regulation treats you as having identified nothing, unless the 95% exception applies.
Because the window is short, many sellers name a backup. An interest in a Delaware statutory trust can sit on the list like other real property, since Rev. Rul. 2004-86 holds that a taxpayer may exchange real property for an interest in a trust structured as that ruling describes.
Related questions
Who do I send the identification to?
To the person obligated to transfer the replacement property to you, or to any other person involved in the exchange who is not you or a disqualified person. The regulation names an intermediary, an escrow agent and a title company as examples.
Does the period restart if a second sale in the same exchange closes later?
No. When one exchange includes several relinquished properties transferred on different dates, the identification period runs from the earliest transfer, under Reg. section 1.1031(k)-1(b)(2)(iii).
Can I change my list during the 45 days?
Yes. A revocation must be a signed writing sent before day 45 ends to the person who received the identification; the regulation's Example 7 holds an oral revocation invalid. After day 45, see changing an identification after the deadline.
Sources
Checked against these publications on September 30, 2026. Rules and figures change; confirm the current version with your CPA or attorney before you act. This page is general information, not tax or legal advice.