Tax-loss harvesting is one of the few legal ways to reduce your tax bill by selling investments at a loss to offset capital gains. Done right, it can save you thousands per year. Done wrong, the IRS will disallow your deductions, or worse, you'll trigger wash sale violations without realizing it.

How Tax-Loss Harvesting Works

When you sell an investment for less than you paid, you realize a capital loss. That loss can offset capital gains from other investments, reducing your taxable income. If your losses exceed your gains, you can deduct up to $3,000 per year against ordinary income and carry forward the rest indefinitely.

The tax rate you're offsetting matters. Short-term capital gains (assets held under one year) are taxed at your ordinary income rate; up to 37% for high earners. Long-term capital gains (held over one year) are taxed at 0%, 15%, or 20% depending on income. Harvesting losses against short-term gains saves you more per dollar than harvesting against long-term gains.

A Quick Example

You sold NVDA earlier this year for a $10,000 short-term gain. You also hold a stock that's down $6,000 from your purchase price. If you sell the loser before year-end:

• Taxable short-term gains drop from $10,000 to $4,000
• At a 32% marginal rate, that's $1,920 saved
• You can immediately buy a similar (but not "substantially identical") investment to maintain your market exposure

The Wash Sale Rule

The IRS has a catch: the wash sale rule. If you sell a security at a loss and buy a "substantially identical" security within 30 days before or after the sale, the loss is disallowed. The disallowed loss gets added to the cost basis of the replacement security; it's not lost forever, but it can't be used now.

What Counts as "Substantially Identical"?

The IRS has never precisely defined this term, which creates a gray area. Here's what's generally understood:

• Clearly identical: Selling and rebuying the same stock or fund
• Likely identical: Selling one S&P 500 ETF (like SPY) and buying another (like VOO); both track the same index. The IRS hasn't ruled definitively, but most tax advisors treat these as substantially identical.
• Likely not identical: Selling a total US market fund and buying a large-cap value fund; different indexes, different holdings, different strategy
• Clearly not identical: Selling an individual stock and buying a broad market ETF that happens to contain that stock

When in doubt, consult a tax professional. The penalty for getting a wash sale wrong is losing the deduction entirely for that tax year.

Common Wash Sale Traps

• Rebuying too soon: Selling a stock and buying it back the next week
• Cross-account purchases: Buying the same security in a different account (IRA, 401k, spouse's account) within the 61-day window
• DRIP reinvestment: Automatic dividend reinvestment in the same security during the wash sale window; easy to miss since it happens automatically
• Nearly identical ETFs: Selling one S&P 500 ETF and buying another from a different provider

Crypto and Tax-Loss Harvesting

As of March 12, 2026, cryptocurrency is generally still treated as property rather than a security for federal tax purposes, so the classic wash sale rule does not currently apply to crypto the same way it applies to stocks.

That means some investors still harvest crypto losses by selling and quickly re-entering the position. But the rule could change, and sloppy records still create filing risk. If you are harvesting crypto losses, track your lots carefully and confirm the current rules before you file.

How to Identify Harvesting Opportunities

To find harvesting opportunities, you need to track the cost basis of every lot you hold. This means knowing exactly what you paid for each purchase, not just the average price.

The IRS allows several cost basis methods. FIFO (First In, First Out) is the default; your oldest shares are sold first. But specific identification lets you choose which lots to sell, targeting the ones with the largest losses. The difference can be significant:

• You bought 100 shares of XYZ at $50 in January and 100 more at $80 in June. It's now trading at $60.
• FIFO: Selling 100 shares realizes a $1,000 gain (sold the $50 lot)
• Specific ID: Selling 100 shares realizes a $2,000 loss (sold the $80 lot)

A $3,000 swing in tax impact; from the same holding, at the same price.

When to Harvest

Year-end is the traditional time (you need to settle trades by December 31), but opportunities exist throughout the year; especially after market downturns. Some investors check quarterly. The key is having real-time visibility into your unrealized gains and losses across all accounts, not just one brokerage.

After significant market corrections (like early 2020 or late 2022), harvesting opportunities are everywhere. Investors who had portfolio-wide visibility were able to harvest far more aggressively than those checking accounts one at a time.

When Harvesting Isn't Worth It

Tax-loss harvesting isn't a free lunch. It makes less sense when:

• Your portfolio is small: If your total losses are under a few hundred dollars, the tax savings may not justify the effort and transaction costs
• You're in a low tax bracket: If your long-term capital gains rate is 0% (single filers under ~$47,000 taxable income in 2026), there's nothing to offset
• Everything is in tax-advantaged accounts: Gains inside IRAs and 401ks aren't taxed, so there's nothing to harvest against
• You'd disrupt a good position: Selling to harvest a $200 loss when you believe in the long-term thesis isn't always the right move; you may lose your position and miss a recovery during the 30-day waiting period

How Clarity Helps

Tracking cost basis, wash sales, and harvesting opportunities across multiple brokerages — including Fidelity, Schwab, and others — and crypto exchanges is hard to do manually. Clarity automates the painful parts:

• FIFO cost basis tracking: Automatic lot-level tracking across all connected accounts; stocks and crypto
• Cross-account lot tracking: Keeps realized and unrealized gain/loss history organized across connected accounts
• Unrealized P&L across all accounts: See every position's gain or loss in one view — not per-brokerage, but total
• Short-term vs. long-term breakdown: Know which gains are taxed at higher short-term rates so you can prioritize harvesting against them

This is one of the strongest product bridges in the tax cluster: readers looking into tax-loss harvesting usually need portfolio-wide lot visibility, not just an explainer. Clarity is most compelling when it can show unrealized losses, holding periods, and cross-account exposure in one place before year-end.

Last reviewed: March 12, 2026. Primary sources: IRS Publication 550, IRS Form 8949, and IRS Topic 409.

Tax-loss harvesting involves individual tax circumstances. This guide is educational — not tax advice. Consult a CPA or tax advisor for decisions specific to your situation.