Wash-Sale Flagger
Paste the same transaction list and this tool flags every sale at a loss that has a purchase of the same symbol inside the window — 30 days before the sale through 30 days after it, both ends and the sale date included, 61 calendar days in all. For each flagged pair it shows the dates, the signed day distance, the size of the loss, how many shares overlap, and — when the replacement purchase covers only part of what you sold — the proportional portion with the arithmetic written out. It flags for review; it does not determine tax treatment. The real rule turns on securities that are substantially identical, which reaches further than an exact symbol match (options, other share classes, funds tracking the same index) and not as far in other cases, and it also reaches across your other accounts, your spouse's accounts and your IRAs — none of which this tool can see. Nothing here says a transaction is or is not a wash sale, and the absence of a flag is never an all-clear: it means only that no same-symbol purchase was found in the window in the data you pasted. No tax rate, no strategy, no advice.
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Worked example
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Inputs
- Lot matching method used to work out each loss
FIFO — oldest lot first / LIFO — newest lot first / HIFO — highest cost per share first / Specific ID — lots named on the sell line
Frequently asked
What exactly is the window?
A purchase counts when its date falls between 30 days before the sale date and 30 days after it, with both ends and the sale date itself included — 61 calendar days in total. The day distance shown next to each purchase is signed: −30 is thirty days before the sale, 0 is the sale date, +30 is thirty days after. A purchase 31 days out on either side is outside the window and is not flagged.
Does a flag mean I have a wash sale?
No. It means this pair is worth reviewing. The tool matches on the exact symbol, which is a rough proxy for the rule's actual test — securities that are substantially identical. That test can catch things with different symbols, such as options on the same stock or two funds tracking the same index, and can exclude things that look similar but are not. Only you, your broker's records and your preparer can settle it.
Does no flag mean I am clear?
No, and the tool refuses to say so. It can only see the lines you pasted. Purchases in another brokerage account, in your spouse's account, or in an IRA can all matter and are invisible here, as are substantially identical securities under a different symbol. Read 'no flag' as 'nothing found in this data', nothing more.
How is a partial replacement handled?
Proportionally, and the arithmetic is printed. If you sold 100 shares at a $500 loss and bought 40 shares back inside the window, 40 of the 100 shares are covered, so $500 × 40 ÷ 100 = $200 is flagged and the remaining $300 is shown separately as not covered by any purchase found in this data. Halves round away from zero, to the cent.
Do reinvested dividends count as purchases?
The tool treats a DRIP line as a purchase and marks it as one in the output, because a small automatic reinvestment inside the window is one of the easiest replacements to miss. Whether a particular reinvestment matters for your return is a question for your preparer.
Why does the matching method change the flags?
Because the loss itself depends on which lots a sale consumed. A sale that shows a loss under FIFO may show a gain under HIFO, and only losses are scanned. The method you pick is stated at the top of the output for exactly that reason.
What happens if one purchase could cover two different loss sales?
It is counted once. Sales are visited oldest first and a purchase already used as a replacement is not reused, so nothing is double-counted. That is this tool's convention for keeping its own arithmetic honest — it is not a statement about how the rule allocates replacements.
Does it adjust my basis or defer the loss?
No. It changes nothing. It produces a list of dates, share counts and amounts to review. Basis adjustments, deferred losses and extended holding periods are all outside what this tool does.
Is there any tax advice here?
None. There is no tax rate, no bracket, no annual limit and no suggestion about what to buy, sell or hold, or when. The tool reads dates and share counts and reports overlaps.