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Tax-loss harvesting means selling an investment for less than its adjusted basis so the loss becomes reportable for tax purposes. You can generally use realized capital losses to offset capital gains, but the loss is currently disallowed when you acquire substantially identical stock or securities during the 30 days before or after the sale. That 61-day period, careful account-wide monitoring, and accurate Form 8949 reporting determine whether a harvest works.
The rules below are U.S.-specific and can change by tax year. They explain the federal mechanics, not individualized tax advice. The “substantially identical” question is fact dependent; consult a qualified tax professional when the replacement investment, account type, or transaction is unusual.
What tax-loss harvesting actually does
A market decline creates an unrealized loss when a security is worth less than its adjusted basis. That decline does not appear as a capital loss on your tax return merely because it is shown on a brokerage statement. The loss becomes realized when you sell or otherwise dispose of the position.
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Why the timing window is called 61 days
The wash-sale period covers the 30 days before the sale, the day of the sale, and the 30 days after it. Counting the sale date produces a 61-day window. A purchase made before you decide to harvest can therefore affect the loss just as much as a purchase made afterward.
How the wash-sale rule works
IRS Schedule D instructions describe a wash sale as selling or otherwise disposing of stock or securities at a loss and, within 30 days before or after that sale, acquiring substantially identical stock or securities or related acquisition rights. The statute says that “no deduction shall be allowed under section 165” for the affected loss. The rule is not limited to a manually entered stock order.
| Activity during the 61-day window | Why it matters | Action to check |
|---|---|---|
| Buying the same stock or fund | Usually the clearest substantially identical purchase | Review every taxable account and retirement account you control |
| Automatic dividend or distribution reinvestment | Reinvestment can buy replacement shares without a new manual order | Temporarily turn off the plan or direct distributions to cash |
| Options or contracts to acquire the security | A right or obligation to acquire substantially identical stock or securities can trigger the rule | Review open calls, puts, rights, warrants, and contracts with a tax adviser |
| Acquisition in an IRA or Roth IRA | IRS instructions include IRA and Roth IRA acquisitions in the wash-sale definition | Include retirement-account transactions in the same calendar review |
| Fully taxable exchange | Acquiring substantially identical stock in a taxable trade can count even without a conventional buy order | Check exchanges, conversions, and corporate-action records |
“Substantially identical” has no universal ETF list
The law does not provide a bright-line taxonomy that labels every pair of exchange-traded funds, mutual funds, stocks, or securities as identical or different. Two investments with different tickers may still be substantially identical under the facts; two investments tracking related but not identical exposures may be treated differently. Index names, holdings, issuer, rights, conversion terms, and the transaction’s legal structure can all matter.
If you need to remain invested, select a replacement that is not substantially identical based on your circumstances and document why you reached that conclusion. Do not treat a different ticker, a different fund family, or a small change in an index label as automatic protection.
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What happens when a wash sale occurs
A disallowed loss is generally deferred rather than erased when replacement shares receive the adjustment. The disallowed amount is added to the basis of the replacement shares. When those shares are later sold, the higher basis changes the later gain or loss. The holding-period treatment can also carry over under the applicable rules, so retain the broker’s lot-level details.
A step-by-step harvesting process
- Export all current tax lots. From every taxable account, obtain the security identifier, number of shares, adjusted basis, proceeds if already sold, acquisition date, and holding period. Include lots held at more than one broker.
- List realized gains and candidate losses. Separate short-term and long-term lots. Compare the size and character of each possible loss with gains already realized and gains you reasonably expect to realize. A large loss is not automatically the best choice if selling it disrupts your allocation or creates a replacement problem.
- Search the 30 days before the intended sale. Look for purchases, dividend reinvestments, automatic investment plans, options, contracts, and IRA or Roth IRA acquisitions of the same or substantially identical security. Check trade dates, not only settlement dates.
- Choose the exact lot. Confirm that the lot’s adjusted basis and holding period match the figures you will report. Selling a high-basis lot can realize a different loss and holding-period character than selling a low-basis lot in the same security.
- Place and preserve the sale record. Save the trade confirmation, execution date, quantity, proceeds, and cost-basis statement. Do not rely solely on a year-end summary that may omit cross-account activity.
- Decide whether to replace the exposure. If you need to maintain market exposure, choose a security that is not substantially identical under your facts. Write down the investment objective, material differences, and date of the analysis. If you cannot make a defensible distinction, remain in cash or obtain professional advice rather than guessing.
- Block accidental repurchases for 30 days after the sale. Review recurring purchases, dividend reinvestment, employer or household accounts you can control, and retirement-account activity. Set reminders for the end of the period.
- Reconcile every account at filing time. Compare broker Form 1099-B data with your own transaction log. Brokers may not identify all cross-account wash sales, so the taxpayer remains responsible for a complete return.
- Report the result. Enter each required transaction on Form 8949, apply the appropriate wash-sale code and adjustment, and carry the resulting totals to Schedule D.
How to choose which losses to harvest
Tax-loss harvesting should be integrated with rebalancing and cash-flow decisions rather than treated as a race to sell the largest red position. Evaluate each candidate on the following axes.
| Decision axis | Questions to answer |
|---|---|
| Loss size and character | How large is the realized loss? Is it short term or long term? What gains can it offset under your current facts? |
| Portfolio exposure | Will selling move the portfolio away from its target allocation? Is a replacement needed to preserve the intended risk exposure? |
| Wash-sale risk | Could any account, reinvestment plan, option, contract, or retirement account acquire substantially identical securities during the window? |
| Trading friction | What commissions, bid-ask spread, market impact, or fund transaction costs will the sale and replacement create? |
| Future basis complexity | Will the replacement create multiple lots, deferred losses, or records that must be tracked across brokers? |
Short-term and long-term lots
Holding-period character is a key comparison point. A short-term loss and a long-term loss can have different effects when matched with short-term or long-term gains. Keep the holding period attached to each lot in your worksheet and verify it against the broker’s records before filing. The federal rules do not make every loss economically equivalent simply because the dollar amount is the same.
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Partial repurchases
If you sell more shares at a loss than you reacquire, only the matched portion is generally subject to wash-sale disallowance. IRS examples allocate the disallowed loss across the replacement lots. For example, if 100 shares are sold at a loss and 40 substantially identical shares are acquired during the window, the affected loss is generally limited to the 40-share portion, with the corresponding adjustment added to those replacement shares’ basis. Use the actual per-share loss and lot quantities; do not divide a total loss arbitrarily when lots have different bases.
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Reporting tax-loss harvesting on Form 8949 and Schedule D
Form 8949 is where you report the individual sales and adjustments. Schedule D summarizes the resulting capital gains and losses after the Form 8949 entries are combined with any transactions that can be reported directly on Schedule D under the filing instructions.
Wash-sale entries
IRS instructions direct taxpayers to use code W for a wash-sale adjustment on Form 8949 and to show the disallowed loss as a positive adjustment. The positive adjustment increases the reported gain or reduces the reported loss to the amount currently allowable. The code and adjustment belong with the affected transaction, not in an unallocated note.
Use the acquisition and disposition information from the broker statement, then add the adjustment required by your complete account review. A broker’s Form 1099-B may show wash-sale amounts in box 1g for specified covered-security circumstances, but the absence of a box 1g amount does not prove that no wash sale occurred.
Reconciling Form 1099-B
- Match each sale by security, trade date, quantity, proceeds, and basis.
- Investigate differences between the broker’s basis and your own records, especially for transferred, inherited, gifted, or older lots.
- Check whether a replacement purchase occurred at another broker or in an IRA or Roth IRA.
- Retain confirmations and calculations supporting any adjustment that the broker did not report.
Check the Schedule D instructions for the tax year you are filing. The 2025 Schedule D instructions and 2026 Form 1099-B instructions should be reviewed against the applicable filing year because form fields and reporting guidance can change.
Retirement accounts and household activity
Acquiring substantially identical stock for an IRA or Roth IRA appears in the IRS wash-sale definition. That means a loss sale in a taxable brokerage account can require review of retirement-account purchases during the 30-day-before/30-day-after period. The practical consequence is asymmetric: if the replacement is in a retirement account, the normal basis-adjustment mechanics may not provide a taxable account lot on which to recover the deferred loss. Because the result can be especially difficult to correct, obtain tax advice before coordinating a taxable loss sale with an IRA transaction.
Also review accounts held by a spouse or other household member when you can identify and control recurring purchases. The safest operational practice is a written account inventory and a calendar covering the entire 61-day period.
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Options and contracts
The wash-sale rules can apply to an option or contract to acquire substantially identical stock or securities. An apparently unrelated options strategy may therefore undermine a harvested loss. Review open positions, exercise notices, assignments, and expirations with someone who understands both the instrument and the tax rules.
Commodity futures and foreign currency
Commodity futures and foreign-currency losses follow different rules discussed in IRS Publication 550. Do not automatically apply the stock-and-securities wash-sale analysis to those instruments.
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Digital assets
IRS instructions state that wash-sale rules generally apply to digital assets that are also stock or securities for tax purposes, including tokenized securities. Ordinary cryptocurrency may receive different treatment because classification matters. Identify what the asset legally represents before assuming that a sale and repurchase is either covered or exempt.
Dealer exception and ordinary-course losses
IRS Schedule D instructions state that a taxpayer generally cannot deduct a wash-sale loss unless the loss was incurred in the ordinary course of the taxpayer’s business as a dealer in stock or securities. This narrow exception is not a general workaround for investors. If you are not operating as a qualifying dealer, plan on the normal wash-sale rules applying.
Records to keep and common failure points
Maintain a lot-level audit trail
Keep trade confirmations, account statements, cost-basis reports, dividend-reinvestment records, option and contract statements, IRA and Roth IRA activity, and your 61-day calendar. For every harvested lot, record the original basis, sale proceeds, realized loss, replacement security analysis, replacement quantity, and any deferred amount added to basis.
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- Treating an unrealized decline as a deduction. No sale or other disposition means no realized capital loss.
- Counting only the 30 days after the sale. The 30 days before the sale count too.
- Checking one account. Wash-sale review must include relevant taxable, IRA, Roth IRA, and automatic-reinvestment activity.
- Assuming a different ticker is safe. Substantially identical is a facts-and-circumstances test.
- Ignoring small reinvestments. Even a fractional replacement purchase can affect the matched portion of a loss.
- Entering a negative adjustment. The disallowed loss is entered as a positive Form 8949 adjustment with code W.
- Relying completely on Form 1099-B. Broker reporting may not capture cross-account transactions or every replacement purchase.
- Forgetting future basis. A deferred loss changes the replacement lot’s basis and must remain in your records until that lot is disposed of.
When harvesting may not be worth doing
A tax benefit is not guaranteed. Selling and replacing a position can create spread and market-impact costs, alter portfolio risk, and increase recordkeeping. A replacement that is too different may leave you underexposed if the market moves before you can return to your target allocation. A replacement that is too similar may create a wash sale. If the loss is small, the transaction costs and administrative burden can exceed its practical value. Compare the expected tax effect with those costs and with your long-term investment plan.
Quick Recap
Bottom-line decision checklist
- The position is actually sold or otherwise disposed of, so the loss is realized.
- The exact lot, adjusted basis, proceeds, and holding period are verified.
- All purchases and acquisition rights in the preceding 30 days have been reviewed.
- All purchases and acquisition rights planned for the following 30 days are blocked or monitored.
- IRA, Roth IRA, reinvestment, option, contract, and household activity have been considered.
- The replacement is demonstrably not substantially identical, or professional advice has been obtained.
- Form 1099-B is reconciled with independent records.
- Form 8949 uses code W and a positive disallowed-loss adjustment where required, with totals carried to Schedule D.
- Any deferred loss and increased replacement basis are documented for the eventual later sale.
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