Tax-Loss Harvesting Before Dec. 31: How the Wash-Sale Rule Works
Learn how tax-loss harvesting works, how the 30-day wash-sale rule applies, and how the $3,000 yearly loss limit fits in.
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Tax-loss harvesting means selling an investment at a loss so the loss can offset capital gains, and up to $3,000 of net loss a year can reduce other income. The catch is the wash-sale rule: if you buy the same or a substantially identical security within 30 days before or after the sale, the loss is not deductible yet. This guide explains how the rule works, how the $3,000 limit applies, and what to check before December 31.
Summary
A capital loss first offsets capital gains. If your capital losses exceed your gains, the IRS says you can claim the lesser of $3,000 ($1,500 if married filing separately) against your income. If your net capital loss is more than that limit, you can carry the loss forward to later years.
The loss only counts in the tax year of the sale, so a 2026 harvest must be sold in 2026.
The wash-sale rule is the part people often miss. A wash sale occurs when you sell stock or securities at a loss and, within 30 days before or after the sale, you buy substantially identical stock or securities. In that case you generally cannot deduct the loss in the year of the sale. The deduction is postponed, not erased.
The Wash-Sale Window
| Action | What happens to the loss |
|---|---|
| Sell at a loss, buy nothing identical for 31 days | Loss can be used, subject to the yearly limit |
| Sell at a loss, buy the same stock within 30 days before or after | Loss is disallowed for now and added to the new shares' cost |
| Sell at a loss, your spouse buys the same stock within 30 days | Treated as a wash sale |
| Sell at a loss, buy a different investment | Ask a tax professional whether it is substantially identical |
| Sell at a loss, buy the same stock after 31 days | Loss can be used, subject to the yearly limit |
The table shows that the window runs both ways. Buying the same stock 30 days before the sale counts just as much as buying it 30 days after. A sale on December 20 has a window from November 20 through January 19, so a purchase in mid-November can already affect a December loss.
When a loss is disallowed because of the wash-sale rules, the disallowed loss is added to the cost of the new shares, and the holding period of the new shares includes the time you held the old ones. The deduction waits until you dispose of the new shares.
A Worked Example
The numbers below are a hypothetical illustration, not market prices. Say you bought 100 shares for $50 each, a total cost of $5,000. You sell all 100 shares at $30 each, for $3,000, and realize a $2,000 loss.
If you buy nothing identical for 31 days, that $2,000 loss can offset capital gains, and any net loss can reduce other income up to the $3,000 limit.
If instead you buy 100 shares of the same stock ten days later at $32 each, for $3,200, the wash-sale rule applies. Your cost in the new shares becomes $3,200 plus the $2,000 disallowed loss, or $5,200. The $2,000 deduction waits until you sell the new shares without triggering another wash sale.
The arithmetic is simple, but the timing decides the outcome. The same sale can be usable now or postponed depending on what you buy in the 61-day period around it, which is 30 days before, the sale day, and 30 days after.
What Counts as Substantially Identical
The same stock of the same company is clearly substantially identical. Beyond that, the line is less clear, so this is the part that needs care. Check with a tax professional before assuming a different fund or security is a safe substitute.
The rule can also reach beyond your own trades. If you sell stock and your spouse or a corporation you control buys substantially identical stock, you may also have a wash sale. Automatic purchases deserve a look too. A dividend reinvestment or an automatic contribution inside the 30-day window could be a purchase you did not plan.
Reporting the Harvest
Your broker may report wash sales on Form 1099-B, but you remain responsible for your own return. Gains and losses from sales of stocks are reported using Form 8949 and Schedule D, so follow the current IRS instructions for those forms. Keep the trade confirmations for both the sale and any repurchase, because the dates decide whether the rule applies.
A missing wash-sale flag on a statement does not mean the loss is automatically usable. Review your own purchase dates across every account you control.
Choosing Order
- List your gains and losses for the year, and work out your net result, keeping the $3,000 yearly limit in mind.
- Check the 30-day window in both directions for each sale, including purchases by your spouse, purchases by a corporation you control, and automatic reinvestments.
- Complete the sale before year end if you want the loss in 2026, then either wait 31 days to buy back or choose a different investment after talking with a tax professional.
Before December 31
- Confirm the sale date, because the loss belongs to the year in which the sale happens.
- Check dividend reinvestment and automatic purchases in every account before you sell.
- If you want to stay invested, ask a tax professional whether a replacement investment is substantially identical to the one you sold.
- Do not assume a loss is usable only because a statement shows no wash sale. Review the dates yourself.
- Keep in mind that any net loss above the yearly limit can be carried forward to later years.
This article is for general information, not financial advice.