Form 3921 Walk-through

Carta makes it easy to file Form 3921. To upgrade to our Form 3921 product, reach out to your sales representative.

Before you generate Form 3921

If your company transferred shares to any person(s) as a result of an Incentive Stock Option (ISO) exercise in the previous calendar year, then the company must file Form 3921 with the Internal Revenue Service. Learn more about Form 3921 here.

  • Jan 31 - Deadline to furnish Copy B to all employees

  • Feb 28 - Deadline to paper file Copy A with the IRS

  • Mar 31 - Deadline to electronically file Copy A with IRS

Before generating Form 3921 on Carta, you will need to request a TCC from the IRS, which is required to generate Copy A of Form 3921. You can request a TCC from the IRS by mail or fax, or online.

Generating Form 3921

After the TCC has been added to the Company > Settings page > Profile tab, you are ready to generate Form 3921 from the Compliance > Form 3921 page, which is able to be generated by a user with Legal Admin or Company Editor permissions. You are still able to generate Form 3921 without a TCC, however, only Copy B and C will be generated. If needed, you can regenerate the form.

Section 6039 of the Internal Revenue Code requires companies to provide Form 3921 Copy B to the employee by January 31 if the employee exercised an incentive stock option (ISO) in the previous year. Companies can deliver this file electronically to the employee through Carta platform. After Copy B is sent to the employees, they can access the PDF through the Carta platform. You can also manually deliver the PDFs of Copy B to the employees.

FAQ: Why does Copy B limit to 2 decimal places for exercise price?

If you are filing electronically, you probably went through some angst last year relating to rounding shares and/or monetary amounts. Publication 1220 was updated this year to specify that a true round should be used on share amounts. There's still no instruction on how monetary values should be rounded, but it would seem reasonable to do the same thing. Each payment field must contain 12 numeric characters. Each payment amount must contain U.S. dollars and cents. The right-most two positions represent cents in the payment amount fields. Reference page 79: p1220.pdf

After you have delivered Copy B

Lastly, Copy A generated by Carta is a .txt file formatted to be uploaded online to the IRS FIRE site by March 31. No changes should be made to the file. Here are steps to upload the Copy A .txt file to the IRS site. 

To file Copy A via paper to the IRS, the form must be requested from the IRS directly for submission, which is due by February 28. Learn more.

If you have questions regarding the generation of Form 3921, please reach out to

If you have questions regarding your TCC or filing with the IRS, please reach out to the IRS directly.

At this time, the IRS Fire site is temporarily unavailable. Learn more

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