Long-term capital gains tax on mutual funds is charged at 0%, 15%, or 20% federally, depending on your taxable income and filing status, when you sell shares you’ve held for more than a year. For the 2026 tax year, a single filer pays nothing on long-term gains up to $49,450 of taxable income; married couples filing jointly get the 0% rate up to $98,900. Higher-income investors may owe an additional 3.8% surtax on top. Your total bill also depends on your cost basis and whether the gain came from your own sale or from a distribution the fund paid out.
The One-Year Holding Period
To qualify for long-term rates, you have to hold the shares for more than one year before selling. The clock starts the day after you buy and runs through the day you sell. Shares bought on March 1, 2025 first qualify for long-term treatment if sold on March 2, 2026 or later. A gain on shares held for a year or less is short-term and gets taxed at your ordinary income rate, which for most middle-income filers is 22% or higher.
That single-day difference can be expensive. Selling a few days early can push a gain from the 15% long-term bracket into your full ordinary rate. If you’re near the anniversary, waiting almost always pays.
2026 Federal Long-Term Capital Gains Rates
Federal law sets three rate tiers. Which one applies depends on your total taxable income for the year, not the size of the gain by itself. The 2026 thresholds are:
- 0% rate: taxable income up to $49,450 (single), $98,900 (married filing jointly), $66,200 (head of household), or $49,450 (married filing separately).
- 15% rate: taxable income above the 0% ceiling up to $545,500 (single), $613,700 (married filing jointly), $579,600 (head of household), or $306,850 (married filing separately).
- 20% rate: taxable income above the 15% ceiling.
These figures adjust for inflation each year.1Internal Revenue Service. Rev. Proc. 2025-32 Your gain stacks on top of your ordinary income when the brackets are applied. If your salary already puts you close to a threshold, even a modest mutual fund gain can push part of the profit into the next tier.
The 3.8% Net Investment Income Tax
Higher-income investors owe an additional 3.8% surtax called the Net Investment Income Tax. It applies to the smaller of your net investment income or the portion of your modified adjusted gross income above a threshold.2Office of the Law Revision Counsel. 26 U.S. Code 1411 – Imposition of Tax The thresholds are $200,000 for single filers, $250,000 for married filing jointly, and $125,000 for married filing separately.3Internal Revenue Service. Questions and Answers on the Net Investment Income Tax
Unlike the capital gains brackets, the NIIT thresholds are not indexed for inflation. A married couple in the top tier can face a combined 23.8% federal rate on a large long-term mutual fund gain.
Capital Gain Distributions You Owe Tax On Without Selling
You can owe long-term capital gains tax even in a year you didn’t sell any shares. When a fund manager sells profitable holdings inside the fund, the fund passes those gains to shareholders as capital gain distributions. They appear in Box 2a of the Form 1099-DIV your brokerage sends in January and are taxed at long-term rates no matter how long you personally held the fund.
Actively managed funds with high turnover tend to generate the largest distributions, sometimes leaving shareholders with a tax bill they didn’t initiate. Index funds and ETFs generally produce fewer of them because they trade less. Checking a fund’s distribution history before buying can prevent a surprise the following April.
Calculating the Gain
Your taxable gain is the sale proceeds minus your adjusted cost basis. Getting the basis right is where most of the work sits, because a mutual fund position typically builds up over years of regular purchases and reinvested distributions.
Cost Basis Methods
The IRS lets you pick among several methods for identifying which shares you sold and at what cost:
- Average cost adds up what you paid for every share and divides by the number of shares to produce a single per-share basis. It’s the default at most brokerages and the simplest to maintain.
- First in, first out treats the oldest shares as sold first. In a rising market, that usually means the lowest-basis shares go first and the reported gain is larger.
- Specific identification lets you pick exactly which lots to sell. You have to designate the lots before the trade settles and get broker confirmation, but it gives you the most control over the tax outcome.
Specific identification takes more effort and can save real money. Selecting your highest-basis lots keeps the taxable gain as small as possible on any given sale.
Reinvested Distributions and Loads
Every dividend or capital gain distribution you reinvested is a new share purchase at that day’s price, and each purchase adds to your total cost basis. Missing reinvested amounts is one of the most common mutual fund tax errors, and it always cuts against you: you report a bigger gain than you actually earned and overpay.
Sales loads, commissions, and transaction fees are also part of what you paid, so they raise the basis too. Front-end loads add to the purchase price; back-end loads reduce the net proceeds. Either way, they shrink the taxable gain.
The Wash Sale Rule
If you sell shares at a loss and buy the same fund or a substantially identical one within 30 days before or after the sale, the IRS disallows the loss. This 61-day window is the wash sale rule.4Office of the Law Revision Counsel. 26 USC 1091 – Loss From Wash Sales of Stock or Securities The disallowed loss isn’t lost permanently; it gets added to the basis of the replacement shares and reduces the gain when you eventually sell those. But you can’t claim the deduction in the current year.
Automatic dividend reinvestment is the usual trap. If a scheduled reinvestment lands in the same fund within 30 days of a loss sale, that triggers the rule. Turning off reinvestment before a planned tax-loss sale avoids it.
Offsetting Gains With Losses
Gains and losses are netted at the end of the year. Short-term gains and losses offset each other first, and long-term gains and losses do the same. If one category ends up net positive and the other net negative, the loss reduces the gain.
If total losses exceed total gains for the year, you can deduct up to $3,000 of the excess ($1,500 for married filing separately) against ordinary income.5Office of the Law Revision Counsel. 26 USC 1211 – Limitation on Capital Losses Anything left over carries forward indefinitely, so a large loss in one year can offset gains you realize much later. That’s the mechanism behind tax-loss harvesting.
Two Situations Where the Rules Change
Two common situations don’t follow the standard capital gains treatment, and it’s worth knowing which side of the line you’re on.
Mutual funds in tax-advantaged accounts. None of the rules above apply to funds held inside a 401(k), traditional IRA, Roth IRA, or similar account. You can buy and sell inside those accounts without triggering any capital gains tax at the time of the trade. The trade-off comes at withdrawal. Traditional accounts tax distributions as ordinary income regardless of how the growth was generated, so a gain that would have been taxed at 15% in a taxable account gets taxed at your full income rate when it comes out. Qualified Roth withdrawals are tax-free.
Inherited shares. When you inherit mutual fund shares, the basis resets to the fair market value on the date the original owner died, wiping out unrealized gains that accumulated during their lifetime.6Office of the Law Revision Counsel. 26 USC 1014 – Basis of Property Acquired From a Decedent If a $50,000 investment had grown to $200,000 by the date of death, your basis starts at $200,000 and you owe capital gains only on growth above that. Inherited shares automatically get long-term treatment no matter how briefly you hold them. If the estate files an estate tax return, an alternate valuation date up to six months after death can be used instead.
State Taxes Are Separate
Federal isn’t the whole bill. Most states tax long-term capital gains at the same rate as ordinary income, with top rates ranging from under 3% to over 13%. A few states have no income tax at all. A smaller group offers a reduced rate or partial exclusion for long-term gains. In high-tax states, combined federal and state taxes on a mutual fund sale can exceed 30%, so checking your state’s treatment before a large sale is worth doing.
Reporting the Gain on Your Return
Your brokerage reports sale proceeds and cost basis to you and the IRS on Form 1099-B. Capital gain distributions from funds you didn’t sell come on Form 1099-DIV.
Sales get transferred to Form 8949, where you list each transaction with dates, proceeds, basis, and any adjustments. Totals from Form 8949 flow to Schedule D of Form 1040, which combines long-term and short-term results into a net gain or loss.7Internal Revenue Service. Instructions for Form 8949 – Sales and Other Dispositions of Capital Assets Capital gain distributions from Form 1099-DIV go straight to Schedule D without passing through Form 8949.
Check that the cost basis on your Form 8949 matches what the broker sent the IRS. Mismatches are one of the most common triggers for IRS notices. If the broker’s basis is wrong, often because reinvested dividends weren’t tracked, you can report the correct figure and note the adjustment on Form 8949, but keep records to back up your number in case the IRS asks.