After-Tax Basis

You invested a hundred grand in Amazon two weeks after the IPO cratered. You held it twenty years and now it's worth about a hundred million. You sell it and start shopping for a ninety-million dollar yacht, with a helicopter pad on top.

To your chagrin, the hundred million dollars you thought you were getting because you live in a high-tax blue state...visits the financial version of Jenny Craig in a violent juice cleanse of cash.

You pay 25% long-term gain, 13.3% state tax, 3.8% for residual Obamacare tax, a city and or county tax here and there, and your hundred million dollars of pre-tax dough has quickly turned into sixty-million dollars. Because yes, you've just paid forty-million in taxes. You'll have to look for the economy-sized yacht.