Updated July 28, 2026. Quick answer: Selling vested shares at a loss can be a wash sale if another vest delivers shares within 30 days before or after. A regular quarterly or monthly vest schedule makes this far more likely than most people expect.
The rule, and why vesting collides with it
A wash sale disallows a loss if you acquire substantially identical stock within 30 days before or after the sale. Most people think of that as a rule about buying. But a vest is an acquisition of shares.
On a monthly vest schedule there is effectively no 61-day window free of an acquisition, which means a loss sale is very likely to be at least partly disallowed.
What happens to the disallowed loss
It is not destroyed — it is added to the basis of the replacement shares and deferred until you sell those. The problem is timing and complexity, not permanent loss.
The wash sale window is 30 days on each side, so the full danger zone is 61 days centred on the sale. Check the vest calendar before harvesting a loss, not after.
What counts as substantially identical
Shares of the same company acquired through a vest, an ESPP purchase, an option exercise, a dividend reinvestment, or an open-market buy can all be replacement stock. So can a purchase in an IRA — and that version is worse, because the disallowed loss is not added to the IRA basis and is simply lost.
Practical sequencing
If you intend to harvest a loss, look at the vest calendar first and find a 61-day window with no acquisition in it. On a quarterly schedule that window exists; on a monthly schedule it usually does not, and the cleaner move is to suspend any reinvestment and accept partial disallowance.
Run your own numbers. Capital-loss harvest helper — net the gains and losses.
Sources
IRC §1091 (wash sales); IRC §1091(d) (basis adjustment to replacement stock).
This states what the cited authority says. It is not tax advice, and equity compensation interacts with the rest of your return in ways a single page cannot see.