™Stock Market University · Research, Taxes & Investor Operations
The Wash-Sale 61-Day Window
Understand the idea. See the connections.
See exactly how the 30 days before and after a loss sale form one easy-to-misread timeline.
The idea to understand
Count the full calendar window correctly and recognize that pre-sale purchases can matter as much as post-sale replacements.
The explanation
The essentials, explained.
Follow the idea, then work through an example. Pause at the self-check whenever you are ready.
Count both directions
The window begins 30 calendar days before the loss sale, includes the sale date and ends 30 calendar days after it. A replacement bought before the sale can therefore matter just as much as one bought afterward.
Calendar days, not trading days
Weekends and market holidays remain part of the count. A purchase on the thirtieth calendar day before or after the sale can fall inside the window.
Every acquisition can matter
Recurring contributions, dividend reinvestment, automatic purchases and option exercises can create replacement shares even when the investor did not place a new manual stock order.
The window tests timing, not the whole rule
Being inside 61 days does not by itself complete the analysis. There must also be a loss and an acquisition of substantially identical stock or securities under the applicable rule.
Optional context & practice
Why this matters
Replacement activity before the loss sale can matter alongside later purchases; the timing window uses calendar days.
Useful vocabulary
Wash sale: A U.S. tax rule that can disallow a current loss when substantially identical stock or securities are acquired within the specified window. Replacement shares: Shares acquired that are evaluated as potential replacements in a wash-sale analysis, subject to timing and substantially-identical requirements. Trade date: The date a transaction is executed, distinct from the later date when settlement finalizes the exchange.
Boundary dates need a complete lot history
Use calendar days on both sides of a loss sale. A purchase on day +30 is inside that side; day +31 is outside it. Being outside for one purchase does not clear every other acquisition. Year-end does not reset the window, and repeated loss sales can create overlapping windows. The timeline tool isolates a date pair rather than preparing a complete tax-lot calculation.
Try it with a hypothetical example
Build a calendar from 30 days before through 30 days after a hypothetical loss sale. Mark weekends and recurring acquisitions explicitly.
A question to think through
A December 20 loss sale is followed by a January 5 acquisition. Does the new tax year remove that purchase from the timing test?
Compare your reasoning
No. It is 16 calendar days later and lies inside the post-sale side, subject to the other wash-sale conditions.
A moment to reflect · optional
Does a replacement bought 20 days before the loss sale fall inside the standard window?
Think through your answer, then compare it with the explanation.
Reveal the explanation
Yes.
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Sources & editorial notes
Reviewed 2026-10-13 · My Market Book editorial team. Examples are hypothetical unless identified as historical. General education, not a personal investment recommendation. Next scheduled review: 2026-11-12, or earlier after a material change. Rule and product sensitive.