Few things frustrate investors more than paying unnecessary taxes on investment gains. While you can’t control market returns, you can control how efficiently you manage taxes. Tax-loss harvesting is one of the most powerful tools available for reducing capital gains tax liability in taxable (non-retirement) accounts.
When done correctly and consistently, tax-loss harvesting can offset gains, lower your current tax bill, and create valuable loss carryforwards for future years, all while keeping your portfolio aligned with your long-term investment plan.
How Capital Gains Taxes Work
Capital gains taxes depend on how long you hold an investment:
- Short-term capital gains (assets held one year or less) are taxed at your ordinary income tax rate.
- Long-term capital gains (assets held more than one year) are taxed at preferential rates of 0%, 15%, or 20%, depending on your taxable income.
- An additional 3.8% Net Investment Income Tax (NIIT) may apply if your modified adjusted gross income exceeds $200,000 (single) or $250,000 (married filing jointly). These thresholds are not indexed for inflation.
State capital gains taxes can add further liability depending on where you live.
What Is Tax-Loss Harvesting?
Tax-loss harvesting is the practice of selling investments that have declined in value to realize a capital loss. That loss can then be used to:
- Offset capital gains dollar-for-dollar in the same tax year.
- Deduct up to $3,000 against ordinary income each year ($1,500 if married filing separately).
- Carry forward any unused losses indefinitely to future tax years.
Without tax-loss harvesting, a large capital loss can take decades to fully utilize against the annual $3,000 ordinary income limit. Offsetting gains, however, can eliminate a significant tax bill in a single year.
The Wash-Sale Rule: The Critical Constraint
The IRS wash-sale rule (IRC Section 1091) prevents investors from selling a security at a loss and immediately buying it back. A wash sale occurs if, within 30 days before or 30 days after the sale (a 61-day window), you:
- Buy substantially identical securities, or
- Acquire a contract or option to buy substantially identical securities.
If a wash sale is triggered, the loss is disallowed for the current year and added to the cost basis of the replacement shares (except when the repurchase occurs in an IRA, where the loss may be permanently lost).
What counts as “substantially identical”?
Selling IBM and buying IBM again clearly violates the rule. Selling one S&P 500 index fund and buying another S&P 500 index fund from a different provider is also considered substantially identical. However, selling an S&P 500 ETF and buying a Russell 1000 ETF (or a total-market fund) is generally allowed, even though the holdings overlap significantly. The positions are highly correlated but not substantially identical.
The same principle applies to actively managed mutual funds: you can sell one fund and buy another with a similar strategy and holdings without triggering a wash sale, provided they are not considered substantially identical.
Practical Tax-Loss Harvesting Strategies
Rebalancing with Tax Efficiency
A core principle of long-term investing is periodic rebalancing, which means selling assets that have grown beyond their target allocation and buying those that have lagged. In taxable accounts, this can create taxable gains. Tax-loss harvesting turns the process into an opportunity: sell losing positions, capture the loss, and reinvest the proceeds into similar (but not identical) holdings that maintain your desired asset allocation.
Actively Managed Mutual Funds
Investors holding actively managed funds outside retirement accounts should be especially attentive. These funds often distribute capital gains to shareholders, even to investors who only recently purchased the fund and did not participate in the gains. Tax-loss harvesting can help offset the tax impact of these unwanted distributions.
Bond Funds and the Cost-Basis Effect
Bond funds present a particularly interesting opportunity because they derive most of their return from the dividend and interest income they produce. While the funds themselves have no stated maturity date, the underlying bonds do.
Imagine an investor who buys a bond fund for diversification but does not need the income at this point in time, so they elect to reinvest all monthly dividend income.
Let’s look at an example using the average cost-per-share methodology for tax purposes.
An account set for reinvestment of dividends and interest buys Mutual Fund XYZ, which pays $40 a month of interest. In this example we also assume an initial purchase of $10,000 and no change to the net asset value of the investment at the end of the period:
| Date | Purchases | Cumulative Cost Basis |
| January | $10,000 | $10,000 |
| February | $40 | $10,040 |
| March | $40 | $10,080 |
| April | $40 | $10,120 |
| May | $40 | $10,160 |
| June | $40 | $10,200 |
| July | $40 | $10,240 |
| August | $40 | $10,280 |
| September | $40 | $10,320 |
| October | $40 | $10,360 |
| November | $40 | $10,400 |
| December | $40 | $10,440 |
| January | $40 | $10,480 |
In this example, your initial $10,000 investment would now be worth $10,480, which is a 4.80% gain. Now let’s say that due to market fluctuation of Bond Fund XYZ, at the end of the year it was only worth $10,200. This would reflect as a loss of –2.67% (because the cost basis is $10,480 minus a current value of $10,200), when in reality it is an actual economic gain of +2.0% ($10,000 now worth $10,200).
If, instead of reinvesting the interest each month, you had directed the interest payments into a money market account, the cost basis would have stayed at the original $10,000. You would have collected $480 of interest, and you could still recognize a taxable loss if the mutual fund were sold at a price below $10,000.
The reason this creates a loss for IRS purposes when dividends are reinvested is that the dividends (which drive most of the investment’s return) were not required to be reinvested. Because you chose to reinvest them, you altered your cost basis every month. In many cases, what appears as a loss on paper may actually be an economic gain. Using the same strategy described earlier, you can sell Bond Fund XYZ and buy a similar (but not identical) Bond Fund ABC, capturing the tax loss while remaining invested and keeping your asset allocation intact.
A Real-World Example
In late 2007, a client invested $1,000,000 just before the market began to decline during the financial crisis. Through disciplined tax-loss harvesting, the client was able to harvest more than $300,000 in tax-loss carryforwards. By late 2010 the portfolio had more than fully recovered to its original $1,000,000 value plus some additional gains. The following year the client sold a rental property that generated a taxable gain of $250,000. As a result of the ongoing tax-loss harvesting program and a disciplined long-term investment approach, the client realized a capital gains tax liability of zero while maintaining the desired investment allocation for continued growth.
Key Benefits of Consistent Tax-Loss Harvesting
- Offsets realized capital gains in the current year
- Creates loss carryforwards that never expire
- Supports disciplined rebalancing without excessive tax cost
- Improves after-tax returns over time
- Works especially well in volatile markets when temporary declines create harvesting opportunities
There is generally little downside to harvesting losses when trading costs are low and the replacement security keeps the portfolio on plan.
Frequently Asked Questions
How much can I deduct against ordinary income?
Up to $3,000 per year ($1,500 if married filing separately). Excess losses carry forward indefinitely.
Does the wash-sale rule apply across different accounts?
Yes. It applies across all your taxable accounts, your spouse’s accounts, and even IRAs in certain circumstances.
Can I harvest losses in a retirement account?
No. Tax-loss harvesting only applies in taxable (non-qualified) accounts.
When is the best time to harvest losses?
Opportunities can arise throughout the year, especially during market declines. Many investors make the mistake of waiting until the final month of the year.
Is tax-loss harvesting suitable for every investor?
It is most valuable for investors with taxable accounts who regularly realize capital gains or expect future gains. Those in the 0% long-term capital gains bracket may sometimes benefit more from harvesting gains to step up basis.
Work With a Fee-Only Advisor
Tax-loss harvesting is a powerful strategy, but execution requires careful attention to the wash-sale rule, lot selection, and overall portfolio design. At Landmark Wealth Management, we integrate tax-efficient strategies into comprehensive financial planning for individuals and families.
About the Author
Joseph M. Favorito, CFP® is a Certified Financial Planner® as well as the founder and managing partner at Landmark Wealth Management, LLC, a fee-only SEC registered investment advisory firm. He specializes in helping individuals and families develop comprehensive financial strategies to achieve their long-term goals.