Process Lab
Free tool · runs in your browser

Wash-sale 30-day window checker

Enter one sale at a loss and up to four purchases of the same stock or ETF, in any account. See the 61-day window, full or partial, the disallowed loss and where the basis adjustment goes.

Educational record-keeping, not tax advice. Confirm with a CPA. Brokers only report wash sales for identical securities in the same account, so purchases in an IRA or another account won't show on your 1099-B.

1The loss sale

2Purchases within about two months of the sale

Result

Worked example

With the defaults (fictional): you sold 100 shares on 2026-03-10 at a $502 loss and bought 100 again on 2026-03-25. The window runs 2026-02-08 to 2026-04-09. The buy is inside it, so it's a full possible wash sale: $502 disallowed and added to the new shares' basis. Change Buy 1 to an IRA and the $502 shows as lost instead. Change the shares to 50 and it becomes a partial wash sale ($251).

How the rule works, including the IRA trap: How wash sales work. For a whole year across accounts, with a 1099-B reconcile, see the Wash-Sale & 1099-B Year-End Workbook.

Every wash-sale, 1099-B and year-end tool, available and coming soon, is in Tax & Records.

Limits: one sale at a time; the earliest replacement shares take the adjustment first; chained wash sales, options, short sales and the carried-over holding period aren't modeled.

FAQ

What does the checker look at?

One loss sale and up to four purchases. It shows the 30-day window before and after the sale, which purchases fall inside it, whether it's a full or partial possible wash sale, the disallowed amount and where the basis adjustment would go.

Does it check IRA purchases?

Yes. Mark a purchase as IRA. The disallowed amount for those shares is shown as lost rather than added to basis (Rev. Rul. 2008-5).

Does it decide what's substantially identical?

No. Enter purchases of the same or a security you and your tax pro treat as substantially identical. That's a judgment call.

Is this tax advice?

No. It's an educational record-keeping helper. Confirm with a CPA.