Form 3921 ISO Reporting
Complete and accurate reporting of incentive stock option exercises. We handle all IRS filings and employee notifications by the January 31st deadline.
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Why Form 3921 Matters
Every corporation must file Form 3921 for each incentive stock option (ISO) exercise during the calendar year. Failure to file correctly and on time can result in IRS penalties up to $340 per form.
Who Must File
Any corporation that transfers stock to an employee or former employee pursuant to their exercise of an incentive stock option (ISO) under Section 422(b) must file Form 3921. This applies to each ISO exercise, not just once per employee.
Electronic Filing Mandate
Companies filing 10 or more Forms 3921 (or combination with Forms 3922 and other information returns) in a year must file electronically. This threshold was significantly reduced from 250 forms in recent years.
IRIS System Transition
For 2026 filings, companies can use either FIRE or IRIS systems. Starting in 2027, all Forms 3921 must be filed through the IRS Information Returns Intake System (IRIS). Companies should begin transitioning to IRIS now.
How It Works
Track All ISO Exercises Throughout the Year
Maintain detailed records of every ISO exercise event as it occurs during the calendar year.
- Date the option was originally granted
- Date the option was exercised
- Exercise price per share
- Fair market value (FMV) per share on exercise date
- Number of shares transferred
- Employee's name, address, and Social Security Number
Prepare Forms by January (for Jan 31 Deadline)
Complete Form 3921 for each ISO exercise that occurred during the prior calendar year.
- Box 1: Enter date option was granted
- Box 2: Enter date option was exercised
- Box 3: Enter exercise price per share
- Box 4: Enter FMV per share on exercise date
- Box 5: Enter number of shares transferred
- Box 6: Corporation info (if different from transferor)
- Transferor section: Company name, address, EIN
- Employee section: Name, address, SSN
Distribute to Employees by January 31
Provide Copy B of Form 3921 to each employee who exercised ISOs during the prior year.
- Must be furnished by January 31 (or next business day if weekend/holiday)
- Can be provided electronically with employee consent
- Keep proof of delivery for your records
- Employees need this for their tax returns
File with IRS by Deadline
Submit all Forms 3921 to the IRS using the appropriate filing method and system.
- Paper filing: March 2, 2026 (or next business day)
- Electronic filing: March 31, 2026
- 10+ forms: Must file electronically
- Use IRIS system (FIRE retiring in 2027)
- Obtain Transmitter Control Code (TCC) if needed
Maintain Records
Keep copies of all filed forms and supporting documentation for IRS audit purposes.
- Retain for at least 3 years from filing date
- Keep stock option grant agreements
- Maintain cap table records showing exercises
- Document FMV determinations (409A valuations)
Key Deadlines
Employee Copy Distribution
Furnish Copy B of Form 3921 to each employee who exercised ISOs during the prior year. If January 31 falls on a weekend or holiday, the deadline extends to the next business day.
Applies to: All companies with ISO exercises
Paper Filing Deadline
Deadline for filing Forms 3921 on paper with the IRS (extended to March 3 since March 2 is Sunday).
Applies to: Companies filing fewer than 10 forms on paper
Electronic Filing Deadline
Deadline for filing Forms 3921 electronically through IRIS or FIRE system.
Applies to: Companies filing 10+ forms (mandatory) or choosing e-file
Prepare for 2027 IRIS Transition
FIRE system will retire after 2026 tax year. All filers must transition to IRIS for 2027.
Applies to: All companies (IRIS mandatory starting 2027)
Common Mistakes to Avoid
Missing the January 31st Employee Deadline
IRS penalties up to $340 per form, plus potential employee complaints if they can't file taxes accurately
Set early January reminders to prepare forms. Distribute by January 31st (or next business day if weekend/holiday) to ensure timely delivery. Consider electronic delivery with consent.
Filing Paper When Electronic is Required
Rejection of filing, penalties for non-compliance, and need to refile electronically
If you have 10+ Forms 3921 (or combined with other info returns), you must file electronically. Check your total count across all forms.
Using Incorrect Fair Market Value
IRS notices, employee tax return errors, and potential AMT calculation problems for employees
Use the FMV from your most recent 409A valuation valid on the exercise date. Document the source of FMV for each exercise.
Not Obtaining Transmitter Control Code (TCC)
Cannot file electronically, causing missed deadlines and penalties
Apply for TCC at least 45 days before deadline. Required for electronic filing through IRIS. One-time setup per entity.
Filing One Form for Multiple Exercises
IRS rejection and penalties. Each exercise must have its own Form 3921
File a separate Form 3921 for each ISO exercise event, even if the same employee exercised multiple times. Use account numbers to differentiate.
Not Preparing for IRIS Transition
Unable to file in 2027 when FIRE system retires, causing compliance failures
Start using IRIS for 2026 filings to familiarize yourself with the system. Obtain TCC and set up IRIS account now.
How Finvisor Helps
We manage your Form 3921 reporting from start to finish, ensuring accurate filings and timely compliance with all IRS requirements.
Year-Round Exercise Tracking
We monitor your cap table and track every ISO exercise as it occurs, maintaining detailed records for Form 3921 preparation.
Employee Distribution & IRS Filing
We prepare forms, distribute Copy B to employees by January 31st, and file electronically with the IRS by March 31st.
IRIS System Management
We handle TCC applications, IRIS authentication, and electronic filing—including API integration for high-volume filers (100+ forms).
Frequently Asked Questions
What is Form 3921 and who needs to file it?
Form 3921 is an IRS information return that corporations must file for every incentive stock option (ISO) exercise during the calendar year. If your company has granted ISOs to employees and any employee exercised their options, you must file Form 3921 for each exercise event. This applies even if an employee exercises multiple times—each exercise requires a separate form.
When are Form 3921 filings due?
There are two critical deadlines: (1) January 31 (or next business day if weekend/holiday) to furnish Copy B to employees who exercised ISOs during the prior year, and (2) March 31 for electronic filing with the IRS (or March 2 for paper filing). Companies filing 10 or more forms must file electronically by March 31st. Missing these deadlines can result in penalties up to $340 per form.
How do I file Form 3921 electronically?
For 2026 filings, you can use either the FIRE system or the newer IRIS (Information Returns Intake System). However, FIRE is retiring after the 2026 tax year, so we recommend transitioning to IRIS now. To file electronically, you need: (1) a Transmitter Control Code (TCC) from the IRS (takes up to 45 days to obtain), (2) an IRIS account with ID.me authentication, and (3) your forms prepared in the correct format. Companies with 100+ returns must use IRIS application-to-application APIs.
What information do I need to complete Form 3921?
You'll need six key pieces of information: (1) Date the option was granted, (2) Date the option was exercised, (3) Exercise price per share, (4) Fair market value per share on the exercise date (from your 409A valuation), (5) Number of shares transferred, and (6) Employee's name, address, and Social Security Number. You must also include your company's name, address, and EIN in the transferor section.
Do I need to file Form 3921 for early exercises?
Yes. Form 3921 must be filed for any transfer of stock pursuant to an ISO exercise, including early exercises of unvested options. The form is required even if the stock is subject to a vesting schedule or repurchase right. The key trigger is the stock transfer, not the vesting.
What happens if I miss the filing deadline?
The IRS can assess penalties up to $340 per Form 3921 for negligent failure to file correctly and on time. If you have 50 ISO exercises and miss the deadline, that's potentially $17,000 in penalties. Additionally, employees won't have the information they need for their tax returns, which can cause problems with their AMT calculations and lead to complaints. File as soon as possible if you've missed a deadline.
Can Finvisor handle Form 3921 filing for us?
Yes. We track all ISO exercises throughout the year, prepare Form 3921 for each exercise, distribute copies to employees by January 31st, and file electronically with the IRS through IRIS by March 31st. We manage the TCC application process, handle IRIS authentication, and ensure full compliance. This is included in our compliance management services for companies with equity compensation programs.
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Let us handle your Form 3921 filings and avoid IRS penalties up to $340 per form.