What is IRS Form 3921?
Form 3921 is the information return your company files with the IRS when an employee exercises Incentive Stock Options. Its full name is Exercise of an Incentive Stock Option Under Section 422(b).
The obligation sits with the company, not the person exercising. You file one form per exercise event, so an employee who exercises three times in a year generates three forms.
What is on it
Five figures, one per box:
Box 1 - Grant date
Box 2 - Exercise date
Box 3 - Exercise price per share
Box 4 - Fair market value per share on the exercise date, usually from your 409A valuation
Box 5 - Number of shares transferred
Why your employee wants it
Exercising ISOs can trigger Alternative Minimum Tax, and the gap between boxes 3 and 4 is what drives it. Their copy of the form is how they calculate that, set their cost basis, and track the holding period that decides whether a future sale qualifies for long-term treatment.
US only: Form 3921 applies to US-incorporated companies. It covers Incentive Stock Options only. Non-Qualified Stock Options are not reported on Form 3921.