When it comes to taxes and equity compensation, one scenario is so dangerous we give it its own section.
danger If you have received an ISO, exercising it may unexpectedly trigger a big AMT bill—even before you actually make any money on a sale! If there is a large spread between the strike price and the 409A valuation, you are potentially on the hook for an enormous tax bill, even if you can’t sell the stock. This has pushed people into bankruptcy. It also caused Congress to grant a one-time forgiveness, the odds of which happening again are very low.
Definition The catastrophic scenario where exercising ISOs triggers a large AMT bill, with no ability to sell the stock to pay taxes, is sometimes called the AMT trap. This infamous problem has trapped many employees and bankrupted people during past dot-com busts. Now more people know about it, but it’s still a significant obstacle to plan around.
new In 2017, Congress passed the Tax Cuts and Jobs Act (TCJA), which increases AMT exemptions and their phaseout thresholds. This means fewer people will be affected by AMT in 2018 than in prior years.*