How Much Tax on a $500,000 Capital Gain: $94,805, Not $119,000.

A couple in their fifties sells a stock position they started building in 2007. The gain is $500,000, they have $200,000 of wages between them, and they file jointly. The number in their head is $119,000, because someone told them the capital gains rate is 23.8%. How much tax on a $500,000 capital gain has an exact answer, and for them it is $94,805 of federal tax. The 23.8% is the top of the schedule. Most sellers never get there.

Long-term gain gets its own rate schedule under IRC §1(h), but the schedule is never applied to the gain by itself. Ordinary income fills the brackets first and the gain sits on top of it, and the breakpoints are measured in total taxable income rather than in gain. For 2026, under Rev. Proc. 2025-32, a married couple filing jointly pays 0% on net capital gain while taxable income stays under $98,900, 15% from there to $613,700, and 20% above that. A single filer's two lines are $49,450 and $545,500.

So wages you already paid tax on change what the sale costs. The $200,000 of wages here, less the 2026 standard deduction of $32,200, leaves $167,800 of ordinary taxable income. The 0% bracket is spent before the gain is counted at all. The first $445,900 of gain then rides at 15% and the last $54,100 at 20%, because the stack crosses $613,700 on the way up. Take the wages away and the same $500,000 pays nothing on the first $98,900 and 15% on the rest, which is $29,970 less federal tax on an identical sale.

IRC §1411 adds 3.8% on the lesser of net investment income or modified adjusted gross income over $250,000 on a joint return, $200,000 single, and $125,000 married filing separately. Those thresholds were written into the statute in 2010 and have never been indexed, so they drift down the income scale every year on their own. Capital gain is net investment income and wages are not, but wages still count toward the MAGI test. This couple's MAGI is $700,000, the excess over $250,000 is $450,000, and 3.8% of that is $17,100, reported on Form 8960. Nothing withholds it and no broker mentions it.

§1222(3) requires more than one year. Fall short and the gain is short-term, taxed at ordinary rates topping out at 37%, and the 3.8% still applies. Run the same sale short-term and the federal cost is $162,029 instead of $94,805. The holding period is worth $67,224 here, which is the best-paid patience available in the tax code.

Two other categories carry their own maximum rates, and §1(h) taxes them before the 0, 15, and 20 stack. Depreciation claimed on a rental comes back as unrecaptured §1250 gain at a maximum of 25% under §1(h)(1)(E), which is the most common reason a projected 15% turns into something worse; the list of ways to avoid depreciation recapture is shorter than most sellers expect. Collectibles, meaning art, coins, and metals, cap at 28% under §1(h)(4).

• –Basis. Every improvement, commission, and reinvested dividend you can document raises basis and cuts the gain dollar for dollar. Property inherited from a decedent resets to date-of-death value under §1014, which is why selling an inherited house often produces almost no gain at all.
• –Losses. Capital losses offset capital gains without limit, and the $3,000 a year cap of §1211(b) applies only to what is left over after the gains are gone. A loss harvested in December counts against a gain realized the previous March.
• –Qualified small business stock. Stock in a C corporation meeting §1202 can exclude a large share of the gain, and the act signed July 4, 2025 rewrote the holding period, the per-issuer cap, and the gross-assets test, so the QSBS math is different now for stock acquired after that date.
• –Timing. Closing in January instead of December, or using the installment method of §453, runs the gain up the bracket schedule twice instead of once. On these facts, splitting $500,000 across two years saves the entire 20% slice.

What does not move it is reinvesting the proceeds. The gain is realized when the asset is sold, and buying something else the next day is a separate transaction the code does not connect to the first one. The exceptions are narrow and specific: a §1031 exchange, which since 2018 covers real property only, a §1045 rollover into other qualified small business stock within 60 days, and a qualified opportunity fund, where a 2026 gain currently defers only to December 31, 2026 and waiting for the 2027 rules is usually the better trade.

§6654 prices tax quarter by quarter. A sale that closed in September belongs to the installment that was due September 15, and settling the whole thing with the return in April leaves penalty interest running from then, at 7% a year compounded daily for the quarter beginning October 1, 2026 under Rev. Rul. 2026-15. The prior-year safe harbor is the clean way out: pay in 110% of your total 2025 tax if your 2025 adjusted gross income was over $150,000, or 100% of it if it was not, and §6654(d)(1)(B) and (C) shut the penalty off no matter what the gain turns out to owe. The safe harbor calculator runs that number.

Two mechanics are worth knowing. Withholding counts as paid evenly across the year under §6654(g)(1) regardless of the month it came out, so if you still have a paycheck, raising line 4(c) of Form W-4 cures a shortfall dating back to the spring in a way that a January estimate cannot. And when the gain lands in one quarter, the annualized income installment method on Schedule AI of Form 2210 sizes the earlier installments to the income you actually had by then, which is the difference between a penalty and none on a December closing.