I think it's even narrower than you point out, as it should be 250K of gains, not just of stock sales. If I, for example, sell 260K of an index fund that I bou

I think it's even narrower than you point out, as it should be 250K of gains, not just of stock sales. If I, for example, sell 260K of an index fund that I bought for 240K, I shouldn't owe this tax. However, if I sell 260K of stock that I got at basically 0 monetary cost as a company founder, then I'd owe the tax.