Wash Sale Calculator
Enter a sale at a loss and the purchases around it. This works out how much of the loss the wash sale rule would disallow on the figures you enter, how much survives, and what the replacement shares’ basis becomes. Free, no signup.
What this assumes
One sale, of one tax lot. The split below is proportional, which is only the right answer when every share sold was bought at the same price, so do not enter a sale that drew on two lots at different prices. Every purchase entered is treated as the same or a substantially identical security, still held. The IRS has never defined that term for funds, and nothing here tests it. The figures are arithmetic on what you type, not a reading of your brokerage records. Estimates only, not tax advice.
The sale at a loss
Purchases of the same security
Anything bought in the 30 days before the sale, on the sale date, or in the 30 days after. Include dividend reinvestments and purchases in other accounts, including a spouse’s: the rule is tested across everything one taxpayer owns, not per account.
The whole loss is disallowed
Loss realized
$1,000.00
100 shares sold.
Disallowed
$1,000.00
100 of 100 shares replaced inside the window.
Still deductible
$0.00
Before the annual cap on losses that exceed your gains: $3,000, or $1,500 if married filing separately, under IRC §1211(b).
The 61-day window for this sale
2026-05-16 through 2026-07-15
A purchase dated 2026-07-16 or later sits outside this sale’s window. That is not a clearance. A different sale carries its own window, a substantially identical security counts as the same one, and purchases in accounts you have not accounted for count too.
What the replacement shares cost you now
| Bought | Replacement shares | Paid | Loss added | New basis |
|---|---|---|---|---|
| 2026-06-20 | 100 | $4,200.00 | $1,000.00 | $5,200.00 |
The part a calculator cannot do
This page prices a sale you already know about. The harder question is which purchases exist across every account you hold, because the rule is tested on all of them at once and no single statement shows them together. Helm reads the transactions in the accounts you connect and screens harvestable losses against purchases in the 30 days before, retirement accounts included. It cannot see the 30 days after, which have not happened yet, and it cannot see accounts you have not connected.
Screen your own accountsWhat the wash sale rule does
IRC §1091 disallows a loss on a sale of stock or securities when you acquire the same or a substantially identical security within 30 days before or 30 days after that sale. With the sale date itself, that is a 61-day window. The loss does not vanish in the ordinary case: §1091(d) adds the disallowed amount to the basis of the shares you bought, so it comes back when you eventually sell those. The rule delays the deduction rather than cancelling it.
How the disallowed amount is worked out
It is proportional. Sell 100 shares at a $1,000 loss and buy 40 back inside the window, and 40 percent of the loss is disallowed, leaving $600 deductible. Buy all 100 back and the whole loss is out. Buy 150 back and still only 100 shares count as replacement property, matched against the shares sold in order of acquisition under Reg. §1.1091-1(b). The disallowance is capped at the loss.
The IRA version is worse
Buying the replacement inside an IRA or Roth IRA is the one case where the loss is not deferred. Under Rev. Rul. 2008-5 the loss on the taxable sale is disallowed and your basis in the IRA is not increased, so there is nowhere for the deduction to come back from. An automatic contribution or a standing order inside a retirement account can do this without any deliberate repurchase.
The holding period follows the shares
Under IRC §1223(3) the replacement shares inherit the period you held the shares you sold. A lot you bought yesterday can already be long term if the position it replaced was held for years. This cuts both ways and is easy to miss, because a brokerage statement usually shows the purchase date rather than the tacked holding period.
What no calculator can tell you
Two things. First, whether two securities are substantially identical: the IRS has never defined the term for funds, and two different index funds tracking the same index have never been ruled on. Second, what you actually bought. §1091 is tested across everything one taxpayer owns, so a dividend reinvestment in an account you forgot about, or a purchase by a spouse, counts the same as a deliberate repurchase. A calculation is only as complete as the list of purchases behind it.
Screening a whole book instead of one sale
This page prices a sale you already know about. Helm works the other direction: it reads the transactions in the accounts you connect, finds positions carrying a loss, and screens each one against purchases in the previous 30 days across every linked account, retirement accounts included. The forward half of the window is unknowable, since those purchases have not happened yet, and any account you have not connected stays invisible. Both limits are stated on the result rather than buried.