Navigating Incentive Stock Options: Key Considerations for Exercise and Sale Decisions

Incentive Stock Options come with a lot of moving parts — tax implications, timing decisions, cash flow considerations. Everyone’s situation is different, and this isn’t specific advice, but I want to walk through how ISOs work and some of the key tax concepts that come into play when you’re deciding what to do with them.

What is a stock option?  A stock option gives you the ability to buy a stock (in this case, your company’s stock), at a designated price.  This designated price is generally known as the strike price or exercise price.  If your exercise price is $5, you are paying $5 to buy 1 share.

The financial incentive to exercise your stock option comes when the fair market value of the stock rises above your strike price. If your strike price is $5 and the FMV rises to $6, you can exercise your option by paying $5 for a $6 stock — an immediate gain of $1 per share. From there, you can hold the stock and let it continue to grow, or sell it and lock in the gain.

As simple as this sounds, there are many different tax calculations that are involved with exercising Incentive Stock Options, and I will write about them below.  

When you exercise your stock option, all you are technically doing is buying your stock at the strike price.  You don’t have the liquidity from selling the stock at this point.  Because of this, the exercise of a stock option is not a taxable event at exercise for regular tax purposes.

When you sell the stock, you will have a capital gain, or loss, from the sale.  If you exercise and immediately sell your stock, your capital gain will be the difference between your exercise price, and the FMV, and will be taxed at your ordinary income rate.  If you hold onto the stock for at least one year after exercise AND two years from your Grant date, your difference between the FMV and exercise price will be taxed at Long Term capital gains rates.

This would all be relatively simple, if Alternative Minimum Tax (AMT) didn’t come into play.  Alternative Minimum Tax is a tax calculation run side by side with your regular return every year.  For most people, it never comes up because they don’t have income that would trigger AMT.  What is often a trigger for paying AMT? Incentive Stock Options.

The gain you make on the exercise of an ISO, aka the difference between the FMV and strike price, multiplied by the number of shares you exercised, is your gain for AMT purposes.  

This gain is put into the AMT calculation, and if your AMT owed is greater than your regular tax owed, you pay whichever is higher.

Clearly this could create an issue if you exercise a large tranche of shares, want to own those shares for at least a year for capital gains purposes, but now you owe AMT on gains you haven’t actually realized yet. 

The good news is that AMT paid on ISO exercises isn’t gone forever. The IRS allows you to carry that AMT forward as a credit, which you can use to reduce your regular tax bill in future years. In years where your regular tax exceeds your tentative minimum tax, you can apply the credit to bring your bill down. Over time, you can recover some or all of the AMT you paid. This doesn’t solve the immediate cash flow problem — you still need the money upfront — but it does mean you’re not permanently out that money.

With some information, we can come to a best guess about whether or not you will owe AMT based on your ISO exercises, and we can plan for situations where we know tax will be owed to have liquidity to be able to make those payments, without needing to sell your stock before you want to.