ETF Tax-Loss Harvesting

ETFs are ideal vehicles for how to tax loss harvest—you can sell at a loss, immediately park proceeds in a similar (but not identical) ETF, and reset your cost basis without triggering a wash-sale violation.

The Basic Mechanic

Tax-loss harvesting is simple in concept: sell a losing position to realize a capital loss, then immediately buy a similar security to stay invested. The loss offsets other capital gains, reducing your tax bill. After 30 days, you can sell the substitute and rebuy your original holding if you wish.

Example: You own 100 shares of a broad U.S. equity ETF (Ticker A) that you bought at $100/share. It has fallen to $75. You have a $2,500 loss ($25 × 100 shares). This year you realized a $3,000 capital gain elsewhere (say, selling a winning position). You can:

1. Sell Ticker A for $7,500, realizing the $2,500 loss.
2. Immediately buy Ticker B, a different broad U.S. equity ETF, for $7,500.
3. Hold Ticker B for 31+ days.
4. After 30 days, sell Ticker B and buy back Ticker A if you wish.

On your tax return, you claim the $2,500 loss against the $3,000 gain, netting $500 in taxable gains instead of $3,000. You stay invested in U.S. equities throughout; you never “miss” a market rally because you were in cash.

Substantially Identical Securities and the Wash-Sale Rule

The wash-sale rule forbids you from claiming a loss if you buy “substantially identical” securities within 30 days before or after the sale. Violate this, and the loss is disallowed; the holding period and purchase date reset.

The IRS does not publish a definitive list of “substantially identical” ETFs. But the consensus among tax professionals is:

• Same index, different ETFs: A Vanguard S&P 500 ETF and an iShares S&P 500 ETF are not substantially identical. Both track the same index, but they hold slightly different securities in slightly different weightings due to sampling differences and management choices. The IRS has not prosecuted cases treating broad-index ETFs as identical.

• Different indexes entirely: A U.S. equity ETF and a Canadian equity ETF are definitely not identical. A bond ETF and an equity ETF are not identical. Even a U.S. equity large-cap ETF and a U.S. equity small-cap ETF are generally not considered identical.

• Same ETF, obviously identical: You cannot harvest a loss on Ticker A, wait one day, and buy Ticker A again. That is a wash sale.

• Ambiguous territory: Sector ETFs (e.g., a technology sector ETF and a software-focused ETF) or commodity ETFs (crude oil vs. an energy sector mix) can blur the line. Tax professionals generally advise caution here.

The safest play for broad-market ETFs is to swap between index-tracking ETFs that track the same index but are issued by different providers. Vanguard-to-iShares or iShares-to-Vanguard swaps are widely regarded as safe and are commonly done by tax professionals and robo-advisors.

Wash-Sale Timing and the 30-Day Window

The wash-sale window extends 30 days before the sale through 30 days after. Many people mistakenly think it is 30 days after the sale; it is actually 61 days total.

• Day 0: You sell the losing ETF (Ticker A).
• Days 1–30 after: You hold the substitute (Ticker B). If you buy Ticker A during this window, wash-sale rules trigger.
• Day 31: You are now free to sell Ticker B and repurchase Ticker A if you wish, with no wash-sale concern.

Important: the 30-day window also reaches backward. If you sold Ticker A on Day 0 and bought it on Days −30 through −1, that prior purchase is considered part of the same wash-sale transaction. This matters if you bought Ticker A in late October and now want to harvest a loss on it in November; you need to ensure you have not bought Ticker A within the prior 30 days.

The Cost of Tracking Divergence

When you harvest a loss by swapping from Ticker A to Ticker B (two different S&P 500 ETFs, say), you are now holding a different security. During the 30-day window, the two will not track perfectly.

Example: Ticker A falls to $75. You sell and buy Ticker B at $75. On Day 10, Ticker A rises to $76 while Ticker B only rises to $75.50 (due to different holdings and fees). You are now underperforming the original position by $0.50 per share on 100 shares: a $50 opportunity cost.

Over the 61-day window, tracking divergence can range from negligible (if the two ETFs are very similar) to significant (if sector allocations or holdings differ materially). The typical gap for same-index swaps is 10–30 basis points annualized, or a few hundred dollars on a six-figure position over a month.

You accept this risk to get the tax benefit. The math usually works: if you are in the 32% or 37% federal tax bracket, a $2,500 loss saves you $800–925 in federal taxes. A $50–100 tracking cost is a bargain.

The Constraint: $3,000 Annual Cap

Important: capital losses can offset capital gains dollar-for-dollar, but once gains are exhausted, you can only use $3,000 of losses to offset ordinary income in a single year.

Any losses beyond $3,000 carry forward indefinitely. You can claim them in future years, year after year, until the losses are exhausted. This is not a “use it or lose it” rule—the loss simply defers to later tax years.

Example: You harvest $10,000 in losses this year but have no gains. You can offset $3,000 of ordinary income (reducing your taxable income by $3,000). The remaining $7,000 loss carries forward to next year, where you can use it again.

This is why tax-loss harvesting is especially valuable if you have realized large gains (e.g., from selling a winning stock or fund). Without harvested losses, those gains are fully taxable. With harvested losses, they are reduced or eliminated.

Practical Steps and Common Mistakes

1. Identify losers: Scan your holdings in January or during any market downturn. Which positions are underwater?

2. Choose a substitute: Identify a different-but-similar ETF. For U.S. equity, iShares and Vanguard S&P 500 ETFs are safe swaps. For bonds, a total bond market ETF and an investment-grade corporate bond ETF might swap.

3. Sell the loser: Realize the loss before year-end (if harvesting for the current tax year).

4. Buy the substitute same day: Do not wait. The wash-sale window begins immediately, and you want to be re-invested without delay.

5. Mark your calendar: 30 days later, you can reverse the trade if you wish (selling Ticker B and rebuying Ticker A).

6. Avoid wash-sale violations: Do not accidentally buy Ticker A during the 30-day window. If you are dollar-cost averaging monthly and Ticker A is your usual buy, you must substitute Ticker B for all purchases during the window.

Common mistake: Selling Ticker A on December 31st, thinking the window is “30 days in the new year,” then buying Ticker A on January 15th. The window includes days before the sale, so the January 15th purchase is a wash-sale violation.

Tax-Loss Harvesting in Tax-Deferred Accounts

This is a critical point: tax-loss harvesting does not work in 401(k) accounts, IRAs, or other tax-deferred vehicles. You have no tax liability in those accounts, so realized losses do not offset anything. Harvesting a loss in a Traditional IRA reduces your balance permanently without any benefit.

Tax-loss harvesting is only valuable in taxable brokerage accounts where you have realized gains or high ordinary income that losses can offset.

See also