Tax-Loss Harvesting Explained: Save Thousands Without Changing Your Investments

Tax-loss harvesting (TLH) is the strangest free lunch in personal finance: you sell an investment at a loss, immediately buy something nearly identical, and the IRS rewards you for it. Done right, it's worth thousands per year for a typical taxable account — and zero for tax-advantaged accounts.

The basic mechanic

Suppose you bought $50,000 of VTI (Vanguard Total Stock Market ETF) at $200/share. The market drops and VTI is now $170/share — your position is worth $42,500, an unrealized loss of $7,500.

Tax-loss harvesting:

1. Sell all 250 shares of VTI at $170 → realize a $7,500 capital loss.
2. Immediately buy a similar but not identical fund — say, ITOT (iShares Core Total US Stock).
3. Your portfolio now holds nearly the same exposure as before, but you've banked $7,500 of tax-deductible loss.

How the loss saves you money

Realized capital losses are deducted from realized capital gains, dollar-for-dollar. If you have no gains, up to $3,000 of net loss can be deducted against ordinary income each year, with the remainder carried forward indefinitely.

At a 24% federal bracket plus 5% state bracket, a $7,500 short-term loss applied against ordinary income saves about $2,175 in tax. Applied against long-term capital gains at 15% federal + 5% state, it saves $1,500.

The wash-sale rule (the trap)

IRS Section 1091 disallows the loss if you buy back the "substantially identical" security within 30 days before or after the sale (61-day total window). Violate this and:

• The loss is disallowed for the current tax year.
• The disallowed loss is added to the cost basis of the replacement shares — eventually recoverable, but you've lost the timing benefit.
• Wash sales can apply across accounts including IRAs and your spouse's accounts.

What counts as "substantially identical"

The IRS hasn't fully clarified, but practitioner consensus:

• Same security: obvious wash. Selling VTI and buying VTI back is identical.
• Same fund, different share class: wash. VTSAX (mutual fund) and VTI (ETF) hold identical portfolios, IRS-flagged risk.
• Different fund tracking the same index: generally not a wash, in practice. ITOT vs VTI track different indices (CRSP vs Russell 3000) — most tax preparers treat as safe.
• Different fund, similar exposure: safe. VTI ↔ SCHB is a textbook safe harvest pair.

Harvest pairs that work

These pairs are generally accepted as "similar but not identical" by mainstream tax practitioners and robo-advisors:

After 31+ days, if you want, you can swap back to the original holding without triggering wash-sale rules. Or just stay in the replacement — both are fine.

When TLH isn't worth it

Tax-advantaged accounts

IRAs, 401(k)s, HSAs, 529s — these have no capital gains tax to harvest against. TLH is irrelevant. Worse, selling at a loss in a tax-advantaged account and buying the equivalent in a taxable account triggers a wash-sale across accounts.

Position is too small

Harvesting $200 of loss saves you $40–$60 in tax — likely below the bid/ask spread cost and your time. Set a floor, e.g. $1,000+ losses only.

You're in the 0% LTCG bracket

For couples filing jointly under ~$94k taxable income, long-term capital gains are taxed at 0%. Harvesting losses to offset 0%-taxed gains saves you nothing. Consider tax-gain harvesting instead.

You plan to give the appreciated assets to charity or heirs

Charitable donations of appreciated stock and step-up basis at death both eliminate capital gains permanently. Selling those positions at a loss converts a step-up opportunity into a realized event.

Tax-loss harvesting at scale

Robo-advisors (Wealthfront, Betterment) and direct-indexing services (Schwab Personalized, Wealthfront, Frec) automate TLH at the individual-stock level. Instead of buying VTI as one position, they hold the underlying ~500 stocks. Some go up, some down, providing many more harvesting opportunities per year.

Marketing claims of "1–2% tax alpha" are usually overstated — peer-reviewed studies suggest the realistic value is 0.3–1.0% annually for someone in a high tax bracket with new money flowing in. Still meaningful: on a $1M portfolio at 0.5% effective alpha, that's $5,000/year of tax savings.

The carryforward trap to know

Any losses you don't use this year carry forward indefinitely on your IRS records. But:

• Carryforward dies with you — your heirs don't inherit it.
• It's state-specific. If you move to a state with different rules (e.g., California treats things differently), tracking gets messy.
• It must be used in chronological order, against the same character (long vs short).

Software (TurboTax, FreeTaxUSA, Wealthfront) handles this — but if you DIY, keep meticulous records.

The end-of-year vs ongoing question

December is when most retail investors think about TLH. But the bigger opportunities come during sharp market corrections — when many positions are simultaneously underwater. A March/April drawdown of 10–15% offers far more harvesting than late-year cleanup of straggling positions.

Set up alerts for individual position losses exceeding $1,000 (or whatever floor makes sense for your portfolio size). Most brokers will let you do this.

Mistakes that cost real money

• Buying replacement shares in your spouse's IRA. Triggers wash sale. The IRS sees household-level activity.
• Reinvesting dividends into the same fund within 30 days of harvesting. Each reinvestment is a small wash that contaminates a portion of the loss.
• Harvesting then immediately re-buying the same position 32 days later just to "get back." Fine, but this is two transactions and possibly a tax inefficiency if the replacement was already comparable. Just stay in the replacement.
• Harvesting positions in 401(k) at retirement to "use the loss." Doesn't work — losses inside qualified plans aren't deductible.

See how much your harvest is worth using our Income Tax Calculator to model your effective bracket.