Wash Sale Calculator (2026)

The loss you thought you booked might wait

Tax-loss harvesting fails when you repurchase substantially identical securities too soon. The wash sale rule disallows the loss and shifts it into replacement share basis instead. Dividend reinvestment, spouse's account purchases, and IRA buys can trigger wash sales you did not intend.

Enter loss sale date, loss amount, replacement purchase dates and shares within the 61-day window. The calculator flags disallowed loss, adjusted basis, and remaining allowable loss for 2026 Schedule D planning.

How wash sales adjust basis

Disallowed loss increases basis of replacement shares by the disallowed amount. Future sale of those shares may recognize lower gain or higher loss because basis is higher. Holding period of replacement shares may include period of original shares—tacking affects short-term vs long-term character on later sale.

How to use the calculator

Step 1 — Enter loss sale

Date, shares, proceeds, basis, computed loss.

Step 2 — List replacement purchases

All purchases of substantially identical securities from 30 days before through 30 days after loss sale, including DRIP shares.

Step 3 — Read disallowed vs allowed loss

Partial wash sales occur when replacement shares are fewer than sold shares—loss is pro-rata disallowed.

Worked example

Sell 100 shares at $3,000 loss on March 10. Buy 100 shares on March 20. Entire $3,000 loss is disallowed; basis of new shares increases by $3,000. Sell new shares later at gain—taxable gain is reduced by embedded basis boost from disallowed loss.

Pair with tax-loss harvesting

Plan harvests in the tax loss harvesting calculator, then verify no wash conflict here before executing trades. Substitute S&P 500 fund with total market fund during window if counsel agrees they are not substantially identical.

IRAs and related accounts

Loss in taxable account plus purchase in IRA within window can disallow loss without increasing IRA basis recoverable on sale—particularly painful trap. Avoid repurchasing inside IRA within 30 days of taxable loss sale of same security.

Crypto note

Model crypto trades in the crypto tax calculator. Wash sale applicability to digital assets has been legislative—treat repurchases conservatively when law requires.

Multiple lots

Specific identification vs FIFO changes which lots match wash sales. Track lot IDs from broker exports; this calculator accepts aggregated loss and replacement amounts you supply.

Common mistakes

• Ignoring automatic dividend reinvestment as a purchase
• Assuming different brokerage accounts are isolated
• Forgetting spouse's purchases count
• Harvesting loss then buying call options on same stock (possible substantially identical issues)

Related tools

Harvest planning: tax loss harvesting calculator. Capital gains: capital gains tax calculator. Investment interest limits: investment interest expense calculator.

Substitute securities and tracking error

Swapping S&P 500 ETF for total market or large-cap value ETF during 31-day window may avoid wash sale while maintaining equity exposure—document non-identical nature for audit file. Automated robo-advisors using substantially identical portfolios may inadvertently wash across accounts you linked—review year-end loss summaries.

Options and warrants on same underlying stock may trigger wash sale analysis beyond simple share repurchase—complex positions need preparer review.

Planning around dividend and ex-dates

Selling before ex-dividend to harvest loss and repurchasing after 31 days avoids wash but forfeits dividend—compare dividend tax cost to loss benefit. Preferred stock of same issuer may be substantially identical to common for wash purposes in aggressive IRS view—conservative planners avoid same issuer equity swaps.

Cryptocurrency wash sale rules: confirm legislative status for your filing year before assuming loss recognition on quick repurchase of same token—policy has shifted and may differ from stock rules.

Married taxpayers wash across accounts and spouses—coordinate trades when one spouse sells and other repurchases within window.

Reading your results for wash sale

The interactive panel above shows a transparent calculation trace in cents—use it to sanity-check inputs before you rely on any number for decisions. Tax software at filing time may differ when every credit, limitation, and state conformity rule is applied in full. Treat output here as structured planning math aligned to 2026 federal reference data where noted, not as e-file output or professional advice.

When your situation includes items this specialized tool simplifies—multiple entities, prior-year carryforwards, treaty elections, or state nonconformity—layer those facts manually or with a preparer. The goal is to narrow uncertainty enough to ask better questions, not to eliminate the need for review when dollars are material.

Recordkeeping that survives scrutiny

Keep source documents (forms, statements, logs, confirmations) that support every input you typed. IRS and state audits often start from third-party reporting; your job is to reconcile 1099s, K-1s, and broker exports to the story you file. Digital backups with dates beat reconstructed spreadsheets created after an notice arrives.

For wash sale, retain worksheets year to year when carryforwards exist—loss carryovers, credit carryforwards, passive loss suspensions, and basis schedules die silently if you change preparers and lose history.

Related tools on this site

Harvest planning: tax loss harvesting calculator. Capital gains: capital gains tax calculator.

2026 federal brackets and payroll context

Ordinary income tax brackets and standard deductions for 2026 follow IRS Rev. Proc. 2025-32 ($16,100 single / $32,200 joint standard deduction; seven marginal rates from 10% to 37%). Social Security tax applies at 6.2% on wages up to the $184,500 wage base; Medicare continues at 1.45% with Additional Medicare Tax above threshold wages. These layers stack independently from specialized rules modeled in this wash sale tool—run the federal income tax calculator when you need the full return picture.

Quarterly estimated tax may be required when withholding does not cover liability—see the quarterly estimated tax calculator. Year-end refund or balance due comparisons belong in the tax refund estimator once withholding and payments are known.

Sources and methodology

Wash sale rules under IRC Section 1091. Educational simplification of lot matching. Not trade execution advice.