Form 3921 is the Internal Revenue Service (IRS) information return that reports a corporation's transfer of stock to a person who exercised an incentive stock option (ISO) described in section 422(b). The corporation completes it; the person who received the stock gets a copy to keep and use when figuring gain or loss on a later sale. On this page you can fill out the form online on FillingPDF and download or print the completed PDF. The current revision of the form and its instructions are published by the IRS.
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What is Form 3921?
Form 3921, Exercise of an Incentive Stock Option Under Section 422(b), is the IRS information return that a corporation files for each transfer of stock to any person made pursuant to that person's exercise of an incentive stock option (ISO) described in section 422(b).
The form records six items: the date the option was granted (box 1), the date it was exercised (box 2), the exercise price per share (box 3), the fair market value (FMV) per share on the exercise date (box 4), the number of shares transferred (box 5) and, when the stock belongs to a corporation other than the transferor, that corporation's name, address and TIN (box 6). It also carries the transferor's and the employee's names, addresses and taxpayer identification numbers (TIN), and an account number.
One sheet holds three copies with the same boxes: Copy A for the Internal Revenue Service Center, Copy B for the employee, and Copy C for the corporation whose stock was transferred, which keeps it. The form is printed with the OMB No. 1545-2129 and the revision Rev. April 2025.
For the employee, the form is the record needed to figure gain or loss in the year the stock is sold or otherwise disposed of. The IRS publishes one set of instructions, Instructions for Forms 3921 and 3922, and the general rules for information returns are in the General Instructions for Certain Information Returns.
Who needs to file Form 3921?
Corporations that transfer stock to a person upon that person's exercise of an incentive stock option described in section 422(b) complete Form 3921, one for each transfer. The IRS employee instructions on the form say the employer (or its transfer agent) may be the one that transferred the stock.
Employees and other option holders do not complete the form. If you exercised an ISO and received stock, you receive Copy B. The instructions on that copy tell you to keep it and use it to figure gain or loss, which you must recognize (report) on your tax return for the year you sell or otherwise dispose of the stock.
Other situations the form addresses:
- If the stock transferred is that of a corporation other than the transferor named in the upper left corner, box 6 identifies that corporation.
- The employee's copy may show only the last four digits of an SSN, ITIN or ATIN. The employer reports your complete TIN to the IRS.
- If you exercise an ISO, you may have to include part of the FMV of the stock in alternative minimum taxable income; see Form 6251 and its instructions.
The form does not describe anyone signing or filing on behalf of another person.
When to file Form 3921
The triggering event is a transfer of stock to a person pursuant to that person's exercise of an incentive stock option under section 422(b): the corporation files one Form 3921 for each such transfer. The form prints no due date of its own. Filing and furnishing deadlines are covered in the Instructions for Forms 3921 and 3922 and in the General Instructions for Certain Information Returns, so check them at www.irs.gov/Form3921 before you prepare the copies.
For the employee who receives Copy B, the relevant timing is different: gain or loss is recognized on your tax return for the year in which you sell or otherwise dispose of the stock, so keep the form until then and use it to figure the result. The IRS agency page for the form lists no recent developments at this time.
How to fill out Form 3921
Mark VOID or CORRECTED if needed
At the top of the form, check the VOID or CORRECTED box only when the form is being voided or is a corrected version of one already issued. Leave both unchecked on an original.
Enter the transferor's information
In the TRANSFEROR'S box, enter the name, street address, city or town, state or province, country, and ZIP or foreign postal code. Enter the transferor's TIN in the TRANSFEROR'S TIN box.
Enter the employee's name and TIN
Fill in the EMPLOYEE'S name and the EMPLOYEE'S TIN. The employee's copy may show only the last four digits, but the employer reports the full TIN to the IRS.
Enter the employee's address
Enter the street address (including apt. no.), then the city or town, state or province, country, and ZIP or foreign postal code.
Add the account number
Use the Account number box for an account or other unique number the employer or transfer agent assigned to distinguish the account.
Enter the dates in boxes 1 and 2
Box 1 is the date the option was granted. Box 2 is the date the option was exercised.
Enter prices in boxes 3 and 4
Box 3 is the exercise price per share. Box 4 is the fair market value per share on the exercise date; both boxes are preceded by a dollar sign.
Enter the shares in box 5
Box 5 is the number of shares of stock transferred to the employee pursuant to the exercise of the option.
Complete box 6 if it applies
If the stock is that of a corporation other than the TRANSFEROR, enter that corporation's name, address and TIN in box 6.
Review, then download the completed PDF
Check each box against your records, then download or print the completed PDF from FillingPDF. Prepare Copies A, B and C as described under How to submit.
How to submit Form 3921
The form is distributed in three copies: Copy A goes to the IRS, Copy B to the employee, and Copy C stays with the corporation.
- Copy A (IRS): marked "For Internal Revenue Service Center". The form directs you to the General Instructions for Certain Information Returns, at www.irs.gov/Form1099, for filing information. The IRS agency page for Form 3921 also lists Form 1096, Annual Summary and Transmittal of U.S. Information Returns, among related products; check the instructions to see when it applies. The form itself prints no mailing address or portal.
- Copy B (employee): marked "For Employee" with the note that the information is being furnished to the IRS. The employee keeps it for their records.
- Copy C (corporation): to be retained by the corporation whose stock has been transferred under section 422(b).
The sheet is printed with the warning "Do Not Cut or Separate Forms on This Page", so follow the instructions for how copies are printed and filed. For substitute forms, the agency page points to Publications 1179 and 1167. FillingPDF lets you fill out and download the PDF; submission follows the channels above.
Common mistakes to avoid
- Cutting or separating the copies on the sheet; the form is marked "Do Not Cut or Separate Forms on This Page".
- Entering the fair market value per share on the grant date in box 4; the box asks for the FMV of a share on the date the option was exercised.
- Leaving box 6 blank when the stock transferred belongs to a corporation other than the transferor named in the upper left corner.
- Mixing up the dates: box 1 is the date the option was granted and box 2 is the date it was exercised.
- Throwing away Copy B; the instructions tell the employee to keep it and use it to figure gain or loss when the stock is sold or otherwise disposed of.
- Assuming the last four digits of a TIN on the employee copy mean the IRS has an incomplete number; the employer reports the complete TIN to the IRS.
- Ignoring a possible alternative minimum tax effect; exercising an ISO may require including part of the stock's FMV in alternative minimum taxable income (Form 6251).
Frequently asked questions
What is Form 3921 used for?
Form 3921 reports a transfer of stock that results from someone exercising an incentive stock option under section 422(b). The corporation files one for each transfer, and the employee uses their copy to figure gain or loss when the stock is later sold or otherwise disposed of.
Who files Form 3921, the employer or the employee?
The corporation files it. The IRS agency page says corporations file this form for each transfer of stock to any person pursuant to that person's ISO exercise. The employee receives Copy B and does not complete the form.
What do I do with Copy B of Form 3921?
Keep it. The instructions on Copy B say to use it to figure gain or loss, which you recognize on your return for the year you sell or otherwise dispose of the stock. For more detail the form refers you to Pub. 525, Taxable and Nontaxable Income.
Does exercising an incentive stock option affect alternative minimum tax?
It may. The employee instructions say that when you exercise an ISO you may have to include part of the stock's fair market value in alternative minimum taxable income. They refer you to Form 6251, Alternative Minimum Tax—Individuals, and its instructions.
What do boxes 3 and 4 on Form 3921 show?
Box 3 shows the exercise price per share of stock. Box 4 shows the fair market value of a share on the date the option was exercised. They are different figures, and box 4 is not the value on the grant date.
Why does my Form 3921 show only part of my SSN?
For your protection, the employee copy may show only the last four digits of your SSN, ITIN or ATIN. The employer has reported your complete TIN to the IRS, so the truncated number does not mean the filing is incomplete.
Can I fill out Form 3921 online on FillingPDF?
Yes. You can fill out the PDF online on FillingPDF and download or print it. FillingPDF is an independent service and does not file the form with the IRS or deliver copies to employees; those steps follow the IRS instructions.
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