100K ISO Limitation on Qualified Stock Option Grants

The $100K Limit (IRS Code Section 422(d)) restricts the amount of Incentive Stock Options (ISOs) that can become exercisable per year to $100,000 (based on strike price). This prevents ISOs from being abused as a tax shelter.
Incentive Stock Options (ISOs), as opposed to Non-qualified Stock Options (NSOs aka NQSOs), are subject to favorable IRS treatment. The main benefit is not having to pay ordinary income tax when you exercise like you do with NSOs. ISOs are still subject to Alternative Minimum Tax (AMT) to prevent wealthy individuals from sheltering all of their income this way.
The $100K Limit prevents people from abusing ISOs as a tax shelter. See this article link for a more complete list of the differences between an ISO and an NSO.
The $100K Limit means that the maximum amount of ISOs that an employee can receive per year is $100,000 per IRS Code Section 422(d).
The calculation for the rule is simple. First, take the total number of options granted then divide by the number of years it will take to fully vest. Most options are not exercisable at inception and typical grants vest over a 4 year period. This will give you the number of options that will become exercisable per year.
Next, multiply the above quantity by the options' strike price. If the resulting value is lower than $100,000, the options are not subject to the rule. If it is higher, any excess options and subsequent grants above the $100K limit must become NSOs. Thus, they are subject to immediate withholding tax at the time of exercise rather than AMT.
One wrinkle is if the grant is eligible for early exercise aka all the options are immediately exercisable. In this case the IRS says that the entire grant is subject to the $100k rule. Early exercise can be great for employees, but it could lead to more NSOs even if you don't exercise early. Note that the same issue arises if the entire grant vests in a single year.
It is very common for employee stock option grants to have a one year cliff when 25% of your grant vests all at once to encourage you to stay with the company at least one year. If your ISO grant was maximized by granting $100K per year, then your company may have inadvertently triggered NSO re-characterization on some of your options. The 100K maximum is based on the tax year in which they options first became exercisable as opposed to the time along the way. For example, let's say you have option to purchase 400,000 shares at a $1 strike price. These vest over a 4 year period with 25% vesting at the 1 year anniversary and the rest vesting 1/48 per month over the remaining 3 years. Let's say that your option grant date anniversary is Jan 15th each year. On Jan 15 of the year of your first anniversary, you'll vest 25% (100,000 shares) but you'll proceed to vest 11 more months of shares during the same tax year. That would be approximately 91,666 more shares which brings your total to 191,666 shares vested during the same tax year. At $1 per share strike price, you exceed the 100K rule by 91,666 shares which would become NSOs while the other 100,000 shares remain ISOs.
Companies commonly add an acceleration clause to the option grant if they are acquired. Acceleration means that some or all of the unvested shares will suddenly vest. The additional vesting is also subject to the 100K Limit. Any accelerated shares exceeding the 100k amount will convert to NSOs.
Those clauses are usually double trigger which means that acceleration only occurs if a second event such as being laid off or demoted also occurs.
If the M&A involves a cash out, then the consequences are greatly reduced. This is because ISOs and NSOs are treated similarly if exercised and immediately sold. For ISOs, this is called a disqualifying disposition.
Exercising stock options can require a lot of capital and time to liquidity can be lengthy. As your shares vest, you may be tempted to sell to recover your original investment or fund other financial needs. However, a sale truncates any possibility of future upside on the shares being sold.
An alternative solution for partial liquidity is to get an advance from ESO Fund. This is an attractive solution since you retain ownership of the stock plus the ability to achieve unlimited upside. Furthermore, if the stock becomes worthless, ESO Fund absorbs the loss, not you. Feel free to reach out using our contact form below if you have any questions.
Written by Jordan Long, Marketing Lead at ESO Fund
Incentive Stock Options (ISOs) have tax advantages, while Non-Qualified Stock Options (NSOs) are taxed as regular income. Click here for more on the differences between ISOs and NSOs.
Vesting means earning the right to exercise stock options over time, often on a schedule set by the company.
ESO Fund helps startup employees exercise their stock options without risking their own cash. We provide non-recourse funding, covering 100% of the exercise cost and taxes, so employees can retain ownership and benefit from future upside. If the company doesn’t succeed, you owe us nothing—we take on all the risk.
Yes, ESO Fund provides non-recourse funding for both Incentive Stock Options (ISOs) and Non-Qualified Stock Options (NSOs).
Equity decisions are complex, but you don’t have to navigate them alone. ESO Fund has been helping employees unlock the value of their hard-earned equity for over a decade. Whether you’re exercising, planning for taxes, or looking for liquidity, we’re here to provide clear, non-recourse funding solutions tailored to your situation.
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