Wash Sale Mechanics
Last verified: 2026-07-03
A wash sale is a tax rule area where casual portfolio notes are not enough. At a high level, it can affect how a loss is treated when an investor sells a security at a loss and buys the same or a substantially identical security within the relevant window described in IRS guidance.
The beginner mistake is thinking the brokerage screen tells the whole story. It may not show every account, every spouse or household-linked situation, every transfer, or every replacement purchase you need to review. This page is a recordkeeping framework, not tax instructions.
Last verified: 2026-07-03. IRS Publication 550 and IRS Topic No. 409 were reachable during this run. Tax-specific questions should be checked against official IRS guidance, broker tax documents, and a qualified tax professional.
The plain-English idea
The rule is designed to stop investors from claiming a loss while quickly keeping essentially the same exposure. The mechanics can get detailed, especially around what counts as substantially identical, which accounts are involved, and how basis may be adjusted.
For practical review, think in three parts:
- ▸Was there a sale at a loss?
- ▸Was there a replacement purchase inside the relevant window?
- ▸Did the record capture the dates, quantities, accounts, and basis notes clearly?
If any answer is unclear, do not guess. Save the documents and verify.
The timeline check
A simple review table helps:
| Date | Action | Account | Quantity | Note |
|---|---|---|---|---|
| Jan 10 | Bought XYZ | Taxable brokerage | 100 | Original lot |
| Mar 5 | Sold XYZ at a loss | Taxable brokerage | 100 | Potential loss event |
| Mar 20 | Bought XYZ again | Taxable brokerage | 100 | Replacement window review |
This table does not decide the tax result by itself. It gives you or your tax preparer the evidence needed to evaluate the rule.
What to track across accounts
Wash-sale review gets messy when the investor uses multiple accounts or automatic investing. Track:
- ▸Taxable brokerage trades.
- ▸Recurring buys and dividend reinvestments.
- ▸Similar ETFs or funds that may need professional review.
- ▸Transfers between brokers.
- ▸Spouse or household account questions where applicable.
- ▸IRA or retirement-account questions that require official guidance.
The safest operational habit is to keep an account-wide calendar of realized losses and planned replacement purchases.
Common mistakes
The first mistake is harvesting a loss and letting an automatic reinvestment repurchase exposure days later. The second is checking only one brokerage account. The third is assuming a similar fund is always clearly different or clearly identical without verification.
Another mistake is using tax language to justify a trade that does not fit the portfolio plan. Tax management should support the plan, not become the plan.
A cleaner workflow
Before selling at a loss, write:
- ▸The position and lot being sold.
- ▸The reason for the sale.
- ▸Whether replacement exposure is planned.
- ▸Any automatic purchases that need to be paused or reviewed.
- ▸The source used for tax-rule verification.
- ▸The date to re-check the record.
After the trade, save confirmations and mark any potentially affected lots.
How Bucko fits
Bucko can help keep the decision trail organized: thesis notes, lot-level context, planned replacement exposure, and review reminders can sit next to the portfolio research. It is a workspace for education and records, not a substitute for IRS guidance or a tax professional.