Harvesting means selling a position at a loss, realising the loss for tax purposes, and reinvesting so the portfolio stays invested. Losses offset gains first; up to $3,000 of net loss can offset ordinary income each year, and the remainder carries forward indefinitely. The wash-sale rule disallows the loss if a substantially identical security is bought within 30 days before or after the sale, across your accounts including IRAs. Harvesting defers tax rather than eliminating it — the replacement's basis is lower — and it does nothing inside retirement accounts.
How it works
Tax-loss harvesting means deliberately selling an investment that is worth less than you paid for it, realising the loss for tax purposes, and reinvesting the proceeds so the portfolio stays invested. The loss becomes usable on the return; the market exposure is maintained.
The ordering rules are fixed. Realised losses first offset realised capital gains of the same character (short-term against short-term, long-term against long-term), then across characters. If net losses remain, up to $3,000 per year can offset ordinary income — a long-standing statutory figure that has not been indexed for inflation. Anything still left carries forward indefinitely to future tax years, where it can offset future gains or, again, up to $3,000 of ordinary income per year.
For a California investor the ordinary-income offset is worth noting, because California taxes both gains and ordinary income at the same marginal rate — the character distinction that matters federally does not change the state result. That is the subject of the capital gains guide.
The wash-sale rule
The rule that makes harvesting a discipline rather than a free lunch: a loss is disallowed if, within 30 days before or 30 days after the sale, you acquire a substantially identical security. That is a 61-day window centerd on the sale date — the "before" half catches people who bought more of a falling position and then sold the older lot.
Points that regularly surprise people:
- The disallowed loss is not destroyed — it is added to the basis of the replacement shares, deferring rather than forfeiting it. Bookkeeping, not catastrophe.
- The window looks across your accounts, including an IRA. A purchase in an IRA can trigger a wash sale against a taxable-account loss, and the disallowed loss in that case is generally lost rather than added to basis — one of the genuinely punitive corners of the rule.
- Automatic dividend reinvestment is a purchase. A reinvested dividend inside the window can trigger the rule on a portion of the loss.
- "Substantially identical" is not fully defined by bright-line rules for every case. Two index funds tracking the same index are widely treated as risky; two funds tracking genuinely different indices are generally treated as not substantially identical. This is a question for a CPA, and the conservative answer is usually the right one.
What harvesting does not do
The most common misunderstanding is that harvesting creates tax savings. It generally creates deferral.
When you sell at a loss and buy a replacement, the replacement has a lower cost basis than the position you sold. That lower basis means a larger gain later, when the replacement is eventually sold. The benefit is real but specific: you use the deduction now and pay the gain later, and money used now is worth more than money used later. In some cases — the position is never sold, or is donated, or the household's future rate is lower — the deferral becomes something closer to a permanent saving. That is a favourable outcome, not the base case.
| Claim | Accurate? | Why |
|---|---|---|
| "It eliminates tax on the loss amount" | No | It defers. Replacement basis is lower, so a larger gain is realised later. |
| "I can deduct all my losses this year" | No | Losses offset gains first; only up to $3,000 of net loss offsets ordinary income per year. |
| "Unused losses expire" | No | Federal carryforward is indefinite for individuals. |
| "I can rebuy the same fund next week" | No | Wash-sale window is 30 days before and after; substantially identical securities disallow the loss. |
| "It works in my IRA too" | No | No taxable gain or loss is recognized inside a retirement account. |
| "It's always worth doing" | No | Costs, tracking error and complexity can exceed the benefit — see below. |
When it is not worth doing
- Retirement accounts. Gains and losses inside an IRA, 401(k) or Roth are not recognized for tax purposes. Harvesting there accomplishes nothing at all.
- Small taxable balances. When the harvestable loss is modest, the value of the deduction can be smaller than the trading costs, bid-ask spreads and the attention required.
- Low-basis positions. A portfolio of long-held winners simply has no losses to harvest. Harvesting is a feature of volatile markets and recent purchases, which is why it is most productive in the years people least enjoy.
- When the replacement is a worse investment. Swapping into a higher-cost or materially different fund to dodge the wash-sale rule can cost more in fees and tracking difference than the deduction is worth. Fees compound in the same direction the whole time — see how fees compound and the fee analyzer.
- When it triggers a decision you would not otherwise make. Harvesting should not change the portfolio's risk profile. If the "harvest" is really a disguised bet, the tax benefit is not what is driving the outcome.
Doing it deliberately
In practice, harvesting works best as a habit rather than an event: reviewing taxable lots when markets fall, checking replacement candidates against the wash-sale rule before trading, turning off automatic reinvestment where it would interfere, tracking carryforwards year to year, and confirming with the CPA that the character of the losses lines up with the gains they are meant to offset.
It also has a limit worth respecting: a portfolio can be harvested only so many times before basis is low across the board and the opportunity is exhausted. Treating it as a permanent yield rather than an opportunistic one leads to disappointment. Our tax-aware investing work builds the checks into the process rather than leaving them to memory. Aduna Capital does not provide tax or legal advice. Nothing here is a recommendation for your situation — consult your CPA or tax attorney before acting.
Common questions
Can I sell at a loss and buy the same fund back in a different account?
Not safely. The wash-sale rule looks across accounts you control, and a purchase of a substantially identical security in another taxable account — or in an IRA — can disallow the loss. The IRA case is worse than the taxable case, because the disallowed loss is generally not added to basis. Check any planned replacement with your CPA first.
Does the $3,000 limit apply per person or per return?
The $3,000 annual ordinary-income offset applies per tax return for most filers, with a lower figure for married-filing-separately. It has not been indexed for inflation, which is why it is one of the few dollar figures safe to state. Carryforward of any excess is indefinite for federal purposes.
Is a different ETF tracking a different index 'substantially identical'?
Generally treated as not substantially identical when the indices are genuinely different, and generally treated as risky when two funds track the same index. There is no exhaustive bright-line list, so the judgement belongs with a CPA who knows the specific holdings — and conservative choices are cheap insurance here.
Does California follow the federal wash-sale and carryforward rules?
California generally conforms to the federal treatment of capital losses and the wash-sale rule, but California's own adjustments and carryforward tracking can differ in specific circumstances. Confirm at ftb.ca.gov and with your CPA rather than assuming the state return mirrors the federal one line for line.
Sources
- IRS, Publication 550, Investment Income and Expenses (wash sales, capital loss limits), irs.gov
- IRS, Topic No. 409, Capital Gains and Losses, irs.gov
- Internal Revenue Code § 1091 (wash sales) and § 1211 (limitation on capital losses)
- California Franchise Tax Board, capital loss and California adjustment guidance, ftb.ca.gov
Want harvesting handled as a process, not a scramble?
We monitor taxable lots, check replacements against the wash-sale rule before trading, and hand your CPA a clean record at year end.