What is the 180-day rule, and do the deadlines ever extend?

The 180 days run concurrently with the 45-day identification period, not after it. Sell on March 1 and your identification is due April 15, with closing due August 28 — regardless of what day of the week those dates fall on. The IRS grants extensions only in rare, formally declared disaster situations.

The lesser-known trap is the tax-return cutoff. If you sell late in the year, your deadline is the earlier of 180 days or the due date of your tax return. Sell in December and your window can shrink to roughly 105 days unless you file an extension for your return. Filing the extension restores the full 180 — an easy fix, but only if you know to do it. Confirm timing with your CPA.

From a lender's chair, the properties that die at day 170 are almost always financing casualties: an appraisal that came back late, a bank committee that met once too few times, a condition nobody could satisfy. Build your financing timeline backward from day 180 with at least three weeks of slack.