Tax StrategyJune 18, 20267 min read

Tax-Loss Harvesting with Index Funds: A Simple Guide

Turn market downturns into a tax advantage. Here\'s how tax-loss harvesting works and when to use it.

What Is Tax-Loss Harvesting?

Tax-loss harvesting (TLH) is the practice of selling an investment that has declined in value to realize a capital loss, then immediately reinvesting in a similar (but not identical) fund to maintain your market exposure. The realized loss can then be used to offset capital gains elsewhere in your portfolio — reducing your tax bill.

It sounds complicated, but the concept is straightforward: you're essentially converting paper losses into real tax savings without changing your long-term investment strategy.

How It Works in Practice

Say you invested $10,000 in VOO (Vanguard S&P 500 ETF) and the market drops 15%. Your holding is now worth $8,500 — a $1,500 paper loss. You sell VOO and immediately buy IVV (iShares S&P 500 ETF), which tracks the identical index. You've harvested a $1,500 tax loss while remaining fully invested in essentially the same portfolio.

The tax benefit: That $1,500 loss can offset $1,500 of capital gains from other investments, reducing your tax bill. If you have no gains to offset, up to $3,000 of losses can be deducted against ordinary income per year — with excess losses carried forward to future years.

The Wash-Sale Rule

The IRS has a critical rule you must follow: you cannot buy a "substantially identical" security within 30 days before or after the sale. Selling VOO and buying VOO back immediately doesn't work — that's a wash sale, and the loss is disallowed.

However, selling VOO and buying IVV (both track the S&P 500 but are different funds from different providers) is generally considered acceptable by most tax professionals, since they're not "substantially identical." Always consult a CPA on your specific situation.

When Tax-Loss Harvesting Makes Sense

  • You have investments in a taxable brokerage account (TLH has no benefit in Roth IRAs or 401(k)s — gains there aren't taxed anyway)
  • You have capital gains elsewhere to offset, or you want the $3,000/year ordinary income deduction
  • The market has dropped, giving you unrealized losses to harvest
  • You're in a moderate or high tax bracket (the benefit is minimal if you pay 0% capital gains tax)

Automated Tax-Loss Harvesting

Some platforms like Betterment and Wealthfront offer automated tax-loss harvesting as a feature. If you're managing your own index fund portfolio, you'll need to do it manually — typically once or twice a year when significant losses appear, or after major market downturns.

Disclaimer: Tax-loss harvesting involves complex tax rules. This article is for educational purposes only and is not tax or financial advice. Always consult a licensed CPA or financial advisor before implementing any tax strategy.
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