The 45-day and 180-day deadlines

When the clocks start

Under Treas. Reg. §1.1031(k)-1(b)(2), the identification period and the exchange period both begin on the date the exchanger transfers the relinquished property, and both end at midnight on the 45th and 180th calendar day that follows. If an exchanger sells more than one relinquished property as part of a single exchange, both periods are measured from the earliest of the transfer dates, not from the last one. There is no separate start date for identification and closing. They are the same day, counted twice.

The count is in calendar days, not business days. Treat the calendar date as the deadline even when it falls on a weekend or holiday; do not rely on the next business day. A closing scheduled for the actual day 180 has to be recorded and funded that day, so a deadline that lands on a weekend in practice pushes exchangers to plan for the last business day before it, even though the regulation itself gives no grace period.

The two periods run together

The most common misreading of the rule is that the 180 days start after the 45 end. They do not. Both periods are measured from day zero, the closing of the sale, so using all 45 days to identify leaves 135 days, not 180, to close on the replacement property. An exchanger who wants the full 180 days available for closing needs to identify early rather than at the deadline.

Day 45: identification

By midnight on the 45th calendar day, the exchanger must identify replacement property in a written document that the exchanger signs, sent to a recipient the regulations allow. Under Treas. Reg. §1.1031(k)-1(c)(2), that is either the person obligated to transfer the replacement property to the exchanger, usually its seller, even if that person is a disqualified person, or any other person involved in the exchange who is not the exchanger or a disqualified person, such as the qualified intermediary, an escrow agent or a title company. An identification written into an exchange agreement signed by all parties also counts. Someone who has acted as the exchanger's agent within the prior two years, such as their own real estate broker, attorney or accountant, is generally a disqualified person (services connected with the exchange itself are not counted), so an identification sent only to them can fail. In practice most exchangers send the identification to their qualified intermediary, and exchange agreements often require it; that requirement comes from the agreement, not from the regulation. The mechanics of what counts as a valid identification, including the three-property, 200 percent and 95 percent rules, are covered in the identification rules guide. Missing day 45 ends the exchange unless replacement property was already received within the 45 days or a disaster or combat-zone postponement applies. Nothing can be added to the list afterward.

Day 180: the exchange period

By midnight on the 180th calendar day, the exchanger must have received the replacement property, which in practice means the purchase has closed. It is not enough to be under contract. The qualified intermediary is assigned into the purchase and wires the exchange funds to that closing.

The 180 days are a ceiling, not a guarantee. Under IRC §1031(a)(3)(B), the exchange period ends at the earlier of day 180 or the due date of the exchanger's federal income tax return for the year the relinquished property was sold, including any extension of that return. For a calendar-year individual, the unextended due date is April 15 of the following year; for many partnerships and S corporations it is March 15. A sale that closes late enough in the year that day 180 would fall after the return's due date is cut short to that earlier date unless the return is put on extension before it is due.

A worked example

Suppose a relinquished property closes on Friday, November 13, 2026. Day zero is that date, and both clocks start together.

Deadlines for a relinquished property closing November 13, 2026

Milestone	Date	Note
Day 0	Friday, November 13, 2026	Sale closes; proceeds go to the qualified intermediary.
Day 45	Monday, December 28, 2026	Signed written identification due to a permitted recipient, usually the qualified intermediary.
Return due (unextended)	Thursday, April 15, 2027	Day 153. Without an extension, this becomes the exchange deadline.
Day 180	Wednesday, May 12, 2027	Available only if the exchanger has filed an extension before April 15, 2027.

Because day 180 in this example falls after the individual exchanger's unextended tax-return due date, reaching the full 180 days requires filing Form 4868, or the corresponding extension for an entity, before April 15. Without that extension, the return's due date, April 15, 2027, becomes the actual exchange deadline. This is the reason a sale that closes anytime after roughly the middle of October deserves an extension conversation with the exchanger's tax advisor well before year end.

What does not extend the deadlines

Neither day 45 nor day 180 moves for reasons that feel like good reasons at the time. Financing that takes longer than expected, a buyer or seller who defaults on the replacement purchase, a title defect discovered late, or a personal illness do not postpone either date. The deadlines are set by statute and regulation, not by the qualified intermediary, and there are no routine extensions available for any of these circumstances.

Disaster relief

Postponement comes from IRS disaster relief (section 7508A, applied to exchanges by Rev. Proc. 2018-58, §17) and from combat-zone relief (section 7508). When the IRS announces relief for a federally declared disaster, a qualifying exchanger's 45-day and 180-day deadlines that fall on or after the disaster date are postponed by 120 days or to the end of the general relief period, whichever is later. The postponement cannot run past the due date, including extensions, of the return for the year of the sale, or past one year. It applies only if the relinquished property was transferred on or before the disaster date and the exchanger is an affected taxpayer or has difficulty meeting a deadline for a reason the revenue procedure lists. Whether a particular announcement applies is fact-specific, so confirm its terms, and your eligibility, with your tax advisor rather than assume relief applies.

Planning around the deadlines

Because neither period allows for routine extensions, the practical safeguard is to begin evaluating replacement property before the relinquished property closes, not after. An exchanger who has toured candidates and has at least a first choice under contract by day zero enters the 45-day period confirming a deal already in motion rather than starting a search from nothing. The deadline calculator generates the exact day 45 and day 180 dates, along with the earlier tax-return cutoff, for any closing date.

Sources

• Internal Revenue Code §1031(a)(3).
• Treas. Reg. §1.1031(k)-1(b)(2) (identification and exchange periods, start and end dates).
• Treas. Reg. §1.1031(k)-1(c)(2) (who may receive the identification) and §1.1031(k)-1(k) (disqualified persons).
• Rev. Proc. 2018-58, §§1 and 17 (postponement of 1031 deadlines under sections 7508 and 7508A).
• IRS Form 8824 and instructions.