Does Selling Part of a Position Trigger a Wash Sale? (w/Examples) + FAQs

This article reflects federal rules as of June 2026 and covers tax year 2025 (the 2026 filing season). State capital-loss treatment is noted where it differs. Tax law changes — confirm current figures before you file. This guide is educational and is not a substitute for advice from a licensed tax professional for your specific situation.

Quick Answer

Yes — selling part of a position can trigger a wash sale, but only the part you replace counts. If you sell some shares at a loss and buy substantially identical shares within 30 days before or after, the loss tied to the replaced shares is disallowed for tax year 2025. The rest of your loss stays deductible.

What This Really Means for Your Loss

When you sell only some of your shares at a loss, the wash sale rule under Section 1091 does not automatically wipe out the whole loss. It only bites the portion of your sold shares that you “replace” with a purchase of the same stock inside the 61-day window — 30 days before the sale, the sale day, and 30 days after. If you do not buy back anything, a partial sale is just a normal sale, and the loss is fully yours to claim. The trap is the replacement purchase, not the partial sale itself.

This matters because a disallowed loss does not vanish — it gets bolted onto the cost basis of the shares you bought, and your holding period rolls over too. Roughly 95% of investors who tax-loss harvest do it near year-end, which is exactly when dividend reinvestments and automatic buys quietly create wash sales, according to year-end planning guidance from J.P. Morgan Private Bank. Miss this and you can lose a deduction you were counting on, sometimes for years.

Here is what you will walk away knowing:

🧩 How a partial sale differs from a full sale when you only rebuy some shares
🧮 The exact share-by-share math the IRS uses to disallow part of a loss
🔁 Which buys count as “substantially identical,” including ETFs, options, and DRIPs
📝 How to report a wash sale on Form 8949 and Schedule D with code “W”
🚫 The seven mistakes that turn a smart tax move into a lost deduction

The Wash Sale Rule, Deconstructed

The wash sale rule exists to stop one specific game: selling a security purely to bank a tax loss while never really giving up your position. Congress wrote it into Section 1091 of the tax code, and the IRS explains it in plain terms in Publication 550. Below are the moving parts, and how each one connects to your partial-sale question.

What Counts as a Wash Sale

A wash sale happens when you sell or trade a security at a loss and, within 30 days before or after that sale, you buy substantially identical securities, acquire them in a taxable trade, or buy a contract or option to acquire them. The federal securities regulator, the SEC’s investor site, lists all three triggers the same way. The consequence is direct: the IRS disallows the loss deduction for the current year. A common misconception is that the rule only covers buying after you sell — it covers the 30 days before the sale too, which is how dividend reinvestments often spring the trap. What you should do is map every buy of that security in the full 61-day window before you claim any loss.

The 61-Day Window

People call it the “30-day rule,” but the real danger zone is 61 days: 30 days before the loss sale, the day of the sale, and 30 days after. These are calendar days, not trading days, so weekends and holidays count. If you sell at a loss on December 15, 2025, your window runs roughly from November 15, 2025 to January 14, 2026, crossing into the next tax year. The consequence of forgetting the “before” side is that a purchase you made weeks earlier — or an automatic reinvestment — can disallow a loss you take later. Mark both ends of the window on a calendar before you sell.

“Substantially Identical” Securities

This is the fuzziest term in the whole rule, and the IRS never gave a clean definition. Publication 550 says stocks of one corporation are ordinarily not substantially identical to stocks of another, but they “may be in some cases,” such as when preferred shares convert into common shares. As Charles Schwab notes, if a security has its own CUSIP number — its unique nine-character ID — it is most likely on the IRS radar. The consequence of guessing wrong is a denied loss plus possible interest if the IRS adjusts your return. The safe move is to replace a sold fund with one tracking a different index, not a near-clone.

The Basis and Holding-Period Adjustment

Here is the part that softens the blow: a disallowed wash sale loss is not lost forever. It is added to the cost basis of the replacement shares, and the holding period of the old shares carries over to the new ones, as H&R Block explains. So you recover the loss later, when you finally sell the replacement shares for good. The big exception, covered below, is buying inside an IRA — there, the loss truly disappears. The action step is to track your adjusted basis carefully, because your broker may not always do it across accounts.

Partial Sale vs. Full Sale: Which Situation Applies to You?

The answer to “does this trigger a wash sale” depends entirely on what you did. Find your situation below, then read the matching example.

You sold some shares at a loss and bought none back. No wash sale. The full loss is deductible.
You sold some shares at a loss and rebought some within 30 days. Partial wash sale. Only the replaced shares are disallowed.
You sold your whole position at a loss and rebought only part of it. Partial wash sale. The loss is disallowed in proportion to the shares you repurchased.
You sold at a loss and rebought an equal or greater amount. Full wash sale. The entire loss is disallowed and rolled into basis.
You rebought in an IRA, a Roth IRA, or your spouse’s account. Wash sale applies, and an IRA repurchase destroys the loss permanently.

How the Math Works on a Partial Sale

The IRS matches replacement shares to loss shares on a share-for-share basis. The number of replacement shares — not the dollar amount — decides how much loss is disallowed. If you sell 100 loss shares and rebuy 40, then 40 shares’ worth of loss is disallowed and 60 shares’ worth survives. This share-counting approach is the heart of every partial-sale question, and it is why a small rebuy only costs you a small piece of your deduction.

Worked Example: Selling Some, Rebuying Some

Suppose you own 200 shares of XYZ bought at $50 each, a $10,000 basis. The price drops to $30. On November 10, 2025, you sell 100 shares for $3,000, locking in a $2,000 loss ($5,000 basis minus $3,000). Eight days later, on November 18, you buy 40 shares of XYZ at $32. Because 40 of your 100 sold shares are now “replaced” inside the window, 40% of the loss is disallowed. That is $800 disallowed and $1,200 still deductible for tax year 2025. The disallowed $800 is added to the basis of the 40 new shares, raising their basis from $1,280 to $2,080. You recover that $800 when you eventually sell the 40 shares outside any wash window.

Worked Example: Selling All, Rebuying Part

Now say you sell your entire 200-share position on December 1, 2025 at $30, for a total loss of $4,000. On December 20, you rebuy 50 shares at $31. Only 50 of the 200 sold shares are replaced, so 25% of the loss — $1,000 — is disallowed, and $3,000 remains deductible. The $1,000 attaches to the 50 replacement shares, lifting their basis from $1,550 to $2,550. The holding period of the original shares carries over, which can help you reach long-term status sooner.

Three Common Scenarios

Each table below shows a real partial-sale setup and its tax result for tax year 2025.

Scenario 1 — Harvest and Hold

Your Move	The Tax Result
Sell 100 of 300 shares at a $1,500 loss, buy nothing back	Full $1,500 loss is deductible — no wash sale
Sell 100 shares at a $1,500 loss, rebuy 100 within 9 days	Entire $1,500 loss disallowed, added to new shares’ basis
Sell 100 shares at a $1,500 loss, rebuy 30 within 9 days	$450 (30%) disallowed; $1,050 deductible

Scenario 2 — The Dividend Reinvestment Trap

Your Move	The Tax Result
Sell 100 shares at a loss; DRIP auto-buys 2 shares 5 days earlier	2 shares’ worth of loss disallowed even though you “sold everything”
Sell 100 shares at a loss; turn DRIP off before the window	Full loss deductible if no other buys occur
Sell at a loss; DRIP reinvests in next quarter inside the window	Partial disallowance based on shares reinvested

Scenario 3 — Crossing Accounts

Your Move	The Tax Result
Sell at a loss in brokerage, rebuy same stock in your IRA	Loss disallowed and permanently lost — no basis recovery
Sell at a loss, spouse buys the same stock in their account	Wash sale applies; loss disallowed and shifts to spouse’s basis
Sell at a loss, rebuy a different-index ETF	No wash sale if the funds are not substantially identical

Named Examples

Maria, the tax-loss harvester. Maria owns 500 shares of a tech stock down $5,000. In December 2025 she sells 250 shares to harvest a $2,500 loss, then waits 31 days before rebuying. Because she bought nothing inside the window, her full $2,500 loss offsets her capital gains. Her patience preserved the entire deduction.

David, the RSU employee. David sells 100 older company shares at a $1,000 loss on March 3, 2026. He forgets that his restricted stock units vested on February 20, delivering 30 new shares. As the Intuit TurboTax community often shows, those vested shares count as a purchase, so 30% of David’s loss — $300 — is disallowed.

Priya, the IRA mistake. Priya sells a fund at a $1,200 loss in her brokerage account, then rebuys the same fund in her Roth IRA two weeks later. Under Revenue Ruling 2008-5, her loss is disallowed and she cannot add it to her IRA basis. The $1,200 is gone for good.

What “Substantially Identical” Catches

The rule reaches far beyond plain common stock. Knowing the edge cases is how you avoid an accidental wash sale.

Mutual funds and ETFs. Two funds tracking the same index can be substantially identical, so swap to a fund tracking a different index. The consequence of swapping S&P 500 fund A for S&P 500 fund B is a likely disallowed loss.
Options and contracts. Buying a call option on the same stock inside the window triggers the rule, because Section 1091 names contracts and options directly.
Dividend reinvestment plans. Automatic DRIP purchases are real buys, and even a tiny reinvested fraction creates a partial wash sale.
Preferred vs. common stock. When preferred shares are convertible into common shares with matching rights, the IRS may treat them as identical.
Crypto, for now. The wash sale rule applies to “stock or securities,” and the IRS has not classified crypto as a security, so crypto is generally not covered for tax year 2025. As a CPA warning notes, Congress has repeatedly proposed closing this gap, so treat it as unsettled and confirm before relying on it.

How to Report a Wash Sale on Your Return

You report a wash sale on Form 8949, then carry the totals to Schedule D, which attaches to your Form 1040. Your broker usually flags the disallowed amount in Box 1g of Form 1099-B. Here is the line-by-line process.

Enter the sale on Form 8949 in the part that matches your holding period — Part I for short-term, Part II for long-term.
Put the disallowed loss in column (g) as a positive number. This is the amount your broker shows in Box 1g, or that you calculated on a partial sale.
Enter code “W” in column (f) to tell the IRS this is a wash sale, as Drake Tax’s guide and Intuit ProConnect both describe.
Let column (h) net out — the proceeds, basis, and the positive adjustment in (g) combine so the disallowed slice is removed from your deductible loss.
Carry the totals to Schedule D on line 1b or 8b (or the relevant line), where they feed your overall capital gain or loss.

The deadline is your regular return due date — April 15, 2026 for tax year 2025, or October 15 with an extension. Missing the code “W” entry can cause the IRS to question a loss your broker already reduced, creating a mismatch and a possible notice. If you have dozens of transactions, most tax software imports the 1099-B and applies code “W” automatically. To learn the form in depth, pair this with a dedicated How to Fill Out Form 8949 guide and a Schedule D walkthrough.

Mistakes to Avoid

Watching only the 30 days after the sale. The window starts 30 days before, so an earlier buy can disallow a later loss.
Forgetting your DRIP is on. Automatic reinvestments are purchases and create silent partial wash sales.
Rebuying in your IRA. Under Revenue Ruling 2008-5, this kills the loss permanently with no basis recovery.
Ignoring your spouse’s trades. A purchase by your spouse or a company you control triggers the rule, per Publication 550.
Swapping near-identical ETFs. Two funds on the same index can be substantially identical and cost you the deduction.
Skipping the basis adjustment. Failing to add the disallowed loss to your replacement shares means you overpay tax when you finally sell.
Trusting one 1099-B across accounts. Brokers track wash sales within one account, not across multiple brokers, so cross-account wash sales are your job to catch.

Do’s and Don’ts

Do wait 31 full days before rebuying to keep your loss clean — patience is the simplest fix.
Do turn off automatic dividend reinvestment around a harvest, so no surprise buy lands in the window.
Do track basis on replacement shares, because that disallowed loss is your future deduction.
Do use a different-index fund as a temporary substitute to stay invested without triggering the rule.
Do check every account, including IRAs and a spouse’s, since the rule reaches across them.
Don’t assume a partial sale is automatically safe — a partial rebuy still disallows part of the loss.
Don’t rebuy the same security in a retirement account, because the loss disappears with no recovery.
Don’t treat crypto as fully settled, since proposed laws could change its status.
Don’t forget the “before” side of the 61-day window.
Don’t omit code “W” on Form 8949, or your reported loss may not match your 1099-B.

Pros and Cons of the Wash Sale Basis Rollover

Pro: The disallowed loss is preserved in the replacement shares’ basis, so you usually recover it later.
Pro: The old holding period carries over, which can move you toward long-term rates faster.
Pro: You can stay invested in a similar asset, avoiding the cost of sitting out of the market.
Pro: A partial rebuy only disallows a partial loss, so small reinvestments cost little.
Pro: Brokers report Box 1g, reducing your manual tracking within a single account.
Con: An IRA repurchase erases the loss entirely, the worst-case outcome.
Con: Tracking basis across multiple brokers falls on you, raising the error risk.
Con: “Substantially identical” is vague, so good-faith swaps can still be challenged.
Con: The recovered loss is deferred, not immediate, hurting current-year planning.
Con: Cross-account and spousal rules make compliance more complex than it looks.

What to Do Next

List every buy of the security across all your accounts for the 61-day window around your loss sale.
Turn off DRIP on positions you plan to harvest, at least a month ahead.
Count replacement shares and apply the share-for-share ratio to find the disallowed portion.
Adjust your basis on the replacement shares by the disallowed amount, and keep the record.
Report it on Form 8949 with code “W” and carry totals to Schedule D by April 15, 2026.
Call a CPA or tax attorney if you have RSUs, cross-account trades, options, or large losses — these are where mistakes get expensive, and professional help often runs a few hundred dollars versus a lost four-figure deduction.

FAQs

Does selling only part of my shares at a loss trigger a wash sale? No — not by itself. A partial sale triggers a wash sale only if you also buy substantially identical shares within 30 days before or after, and then only the replaced portion is disallowed for tax year 2025.

How much of my loss is disallowed on a partial rebuy? The portion equal to the replacement shares. If you sell 100 loss shares and rebuy 40, then 40% of the loss is disallowed and 60% stays deductible.

Is the disallowed loss gone forever? No — in a normal account it is added to the basis of your replacement shares, so you recover it when you sell those shares outside any wash window.

Does the wash sale rule apply if I rebuy in my IRA? Yes, and it is worse. Under Revenue Ruling 2008-5, the loss is disallowed and you get no basis increase, so it disappears permanently.

Do dividend reinvestments cause wash sales? Yes. Automatic DRIP purchases count as buys, so even a small reinvested amount inside the window creates a partial wash sale on a loss you take.

How long do I have to wait to safely rebuy? 31 days. Waiting more than 30 calendar days after the sale puts your purchase outside the window and keeps your loss fully deductible.

Does the wash sale rule apply to crypto? Generally no for tax year 2025, because the IRS treats crypto as property, not a security. Proposed laws could change this, so confirm before relying on it.

Can I sell at a loss and buy a different ETF? Yes, as long as the new fund is not substantially identical. Choosing a fund tracking a different index usually avoids the rule.

What code do I use on Form 8949 for a wash sale? Code “W.” Enter it in column (f) and put the disallowed loss as a positive number in column (g), as the Form 8949 instructions direct.

Does my spouse’s purchase count against me? Yes. A buy of substantially identical securities by your spouse, or a company you control, triggers the rule, per Publication 550.

Do states follow the federal wash sale rule? Mostly yes. Most states that tax capital gains start from federal taxable income, so the federal disallowance flows through; states with no income tax do not tax the gain or loss at all.

What happens if I ignore the rule and claim the full loss? The IRS can adjust your return. Because brokers report disallowed amounts in Box 1g, a mismatch may trigger a notice, additional tax, and interest.

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