Qualified Small Business Stock: The Exclusion, and the Traps That Void It

There's a provision in the tax code that sounds too generous to be real. Section 1202. Hold the right kind of stock in the right kind of company for long enough, sell it, and you pay no federal tax on a very large slice of the gain, potentially millions of dollars, fully exempt. Founders and early employees who qualify keep what everyone else hands to the government.

The catch is that qualifying is a maze. Most people who believe they hold qualified small business stock have never actually confirmed it, and a fair number have quietly disqualified themselves without knowing. The exclusion is real and it's huge. It's also unforgiving, and the moves that lock it in or throw it away happen years before anyone sells. What follows is the map of what earns it and what voids it in silence.

What The Exclusion Actually Is

For stock that qualifies and is held long enough, Section 1202 exempts the gain on a sale from federal income tax, up to a cap. The cap is the greater of two things: a flat dollar figure, or ten times your cost basis in the stock, measured company by company. The flat figure is fifteen million dollars for stock acquired after July 4, 2025, and ten million for stock acquired before then, under whatever rules applied when you bought in. A founder with almost no basis is capped by the flat figure. For someone who put real money in, the ten-times-basis number can run much larger.

Read the cap carefully, because the ten-times-basis alternative is the half nobody uses. An investor who contributes real capital, or a founder whose basis got stepped up in a reorganization, can shelter many multiples of the flat cap on one company. So the exclusion isn't a fixed number. It's a formula, and set up far enough in advance, it can be made much bigger than the headline figure suggests.