The short answer
You prove it with a paper trail built on the day you send the notice: the signed identification itself, evidence of when and how it was sent, a dated acknowledgment from the person who received it, and the settlement statement that fixes day zero. Reg. section 1.1031(k)-1(c)(2) asks whether the signed document was "hand delivered, mailed, telecopied, or otherwise sent before the end of the identification period" to a permitted recipient, so the sending date is what you must show. Form 8824 then asks you to report that date on line 5, and the IRS tells you to keep exchange records until the limitations period runs on the year you sell the replacement.
At a glance
| What must be shown | A signed writing sent to a permitted recipient by midnight on day 45 |
|---|---|
| Sent or received | The regulation tests when it was sent |
| Permitted recipients | The seller of the replacement or another non-disqualified party, such as the intermediary |
| Not enough | Notice only to your own attorney, agent or accountant |
| Form 8824 | Line 5 reports the date of the written identification |
| Record period | Until the limitations period ends for the year you dispose of the replacement |
| Best proof | The recipient's dated, written acknowledgment |
The test is when a signed notice was sent to the right person
The regulation requires a "written document signed by the taxpayer" designating the property, sent before the period ends to either the person obligated to transfer the replacement to you or any other person involved in the exchange who is not a disqualified person. It lists intermediaries, escrow agents and title companies as examples of people involved in the exchange.
The IRS fact sheet FS-2008-18 adds the practical warning: "notice to your attorney, real estate agent, accountant or similar persons acting as your agent is not sufficient." Proof that your broker got the list on day 44 proves nothing useful.
Day 45 ends at midnight, and the count starts the day after your sale; what starts the clock is set by the date ownership passed. Who should receive the notice is covered in who has to receive my identification notice.
Build the file the same day you send the notice
Each piece below answers a different question an examiner may ask: what was identified, when the clock started, when the notice went out, and who got it.
The strongest single item is the recipient's own dated acknowledgment, because it comes from a third party rather than from you. Ask your intermediary to countersign or email back a dated receipt the same day.
- The signed identification, showing the legal description, address or distinguishable name of each property.
- Transmission proof: the fax confirmation sheet, the courier or certified-mail receipt, or the sent email with its full header and attachment.
- The recipient's dated acknowledgment or countersignature.
- The exchange agreement and the relinquished property's settlement statement, which fix day zero.
- Any revocation or amended list, sent the same way, because revocations must also be signed and sent before day 45 ends.
- A calendar printout showing day 45 calculated from the sale date.
What a late or defective notice looks like in an audit
The regulation's examples show identifications that fail. A notice describing "unimproved land located in Hood County with a fair market value not to exceed $100,000" identified nothing. An oral revocation was ignored, so all four listed properties counted and the list blew the limits.
A notice can also fail on timing. A file whose only proof is an unsigned list, a text to your agent, or an email with no timestamp leaves you arguing from memory. If more than three properties were listed and the 200% limit was exceeded, the regulation treats you "as if no replacement property had been identified," subject to narrow exceptions for property already received or the 95% rule.
Never backdate a notice or ask anyone to. The date on line 5 of Form 8824 is part of a signed return, and a late notice is a failed exchange, which is a far smaller problem than a false document.
Worked example: a notice sent at 11:40 p.m. on day 45
Hypothetical dates. You sell on Monday June 1, 2026, so day 45 is Thursday July 16. You sign your list that evening and email a scanned copy to your intermediary at 11:40 p.m.
Because the regulation asks whether the notice was "sent" before the period ended, the email's timestamp is your proof, and the intermediary's reply the next morning confirms receipt. Save the email in its original format with headers, not just a printout.
Whether email counts as a signed writing is its own question; see can I send my identification by email or text. Sending at 11:40 p.m. is legal but leaves no room for a bounced message, so send by midday.
Keep the file for as long as you own the replacement, and longer
The IRS says that for property received in a nontaxable exchange you "must keep the records on the old property, as well as on the new property, until the period of limitations expires for the year in which you dispose of the new property" (IRS, how long should I keep records). For an exchange chain, that can mean decades.
A trust interest listed on your notice needs the same proof as a building. If you exchange again later, your new file starts with this one; see what records to keep for a 1031 audit.
Related questions
Does the intermediary have to receive the notice by day 45, or just have it sent?
The regulation's wording is sent before the end of the identification period. Aim for receipt and a written acknowledgment the same day anyway, so you never have to argue the point.
Is the intermediary's exchange software log enough proof?
It helps, especially if it shows the upload time. Keep your own copy of the signed notice and the confirmation too, because the intermediary's systems may not exist when you are examined.
I mailed the notice on day 44 and it arrived on day 48. Is it timely?
The regulation lists mailing as a method and tests whether the notice was sent before the period ended. Keep the postmark or mailing receipt as your proof of the date sent.
Do I attach the identification notice to my tax return?
Form 8824 asks for the date on line 5; it does not ask you to attach the notice. Keep it in your records.
Can my intermediary send the notice on my behalf?
The regulation requires a document signed by you. Your intermediary can receive it and acknowledge it, but the designation must be yours.
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.