AMT and Incentive Stock Options: What to Know Before You Exercise

Incentive stock options are often described as the best kind of equity. But the best features come with a catch: exercising them can create a tax bill before you have sold any shares. That is the alternative minimum tax at work.

How AMT gets triggered

When you exercise an ISO, the difference between your strike price and the fair market value of the stock is called the bargain element. For regular income tax, that is not taxed at exercise. But for AMT, it is. If the bargain element is large enough, your AMT bill can be far higher than your regular tax bill, and it is due before you sell the stock.

AMT credit and the second year

The good news is that AMT paid on ISO exercise can become a minimum tax credit, which you may recover in later years when your regular tax exceeds your AMT. That means the AMT is often a prepayment, not a permanent loss. Still, the timing can be painful if you exercised a lot of shares and the stock drops.

Qualifying vs. disqualifying disposition

A qualifying disposition means you held the shares for at least two years after grant and one year after exercise. If you do that, the entire gain is taxed as long-term capital gains. A disqualifying disposition means you sell earlier, and the bargain element is taxed as ordinary income. The right choice depends on your cash flow, tax situation, and confidence in the company.

Before you exercise

Before exercising ISOs, estimate the AMT impact, decide whether you can pay it out of pocket, and confirm whether you will qualify for a disposition that matches your tax plan. Many people exercise early in the year to give themselves more time to hold and to react if the stock price changes.

ISOs are powerful, but the tax timing is not optional. A little modeling before you exercise can prevent a large surprise at tax time.