IRS Modernizes 3921 and 3922 Filings with IRIS

The IRS is rolling out significant updates to its electronic filing system for the 1099 series and other information returns—including Form 3921 for incentive stock options (ISOs) and Form 3922 for employee stock purchase plans (ESPPs). Starting in 2027, all Forms 3921 and 3922 must be filed using the new platform.

Here’s a practical overview of what’s changing and what it means for your Section 6039 filings.

FIRE vs. IRIS: What’s the Difference?

The Filing Information Returns Electronically (FIRE) system has been the backbone of IRS electronic filing since the 1980s. It supports Forms 1099, 3921, 3922, and many other information returns—but it’s based on older mainframe technology and requires ASCII file uploads. Until very recently, it was the only way to electronically file Forms 3921 and 3922.

The Information Returns Intake System (IRIS) is the IRS’s modernized platform, designed to replace FIRE. As explained in an article by 1099-Pro, IRIS introduces several upgrades that equity compensation teams—and especially those managing Section 6039 filings—will appreciate, including:

• A web portal for filings of no more than 250 returns. Returns can be entered manually or uploaded via CSV file.
• Real-time error detection for TINs and file formats
• The ability to correct individual returns without having to resubmit the filing
• Separate fields for first, middle, and last names
• Year-round testing (a huge improvement over FIRE’s limited test window)
• Modern XML-based architecture with XML/JSON files and improved security
• APIs for application-to-application filings (instead of manual uploads)

For more information on IRIS, see IRS Publication 5717, Information Returns Intake System (IRIS) Taxpayer Portal User Guide. Also, here is an IRIS 101 slide deck from the IRS that provides a high-level summary of the new system. If you are a provider that needs to build the APIs to submit filings to IRIS, see IRS Publication 5718 Information Returns Intake System (IRIS) Electronic Filing Application to Application (A2A) Specifications.

How Will You Submit Filings via IRIS?

The answer to this question likely depends on the number of returns you need to file.

Only a Few Returns to File

If you only have a handful of returns to file (e.g., a handful of ISO exercises), you can simply manually enter the returns via the IRS web interface; you won’t need to pay for a third-party solution or deal with CSV files.

Your company will need a TCC for IRIS, you’ll need to be authorized to use that TCC, and you’ll need a login to IRIS (through ID.me).

More Than a Handful but Fewer Than 250 Returns to File

If you have enough returns to file that you don’t want to have to manually enter each one but you don’t have more than 250 forms to file, you can create a CSV file and upload it through the IRS web interface. Your equity plan recordkeeping platform might even offer a file in the requisite CSV format. If not, they probably offer an export that includes the information necessary for you to create the file yourself.

Your company will need a TCC for IRIS, you’ll need to be authorized to use that TCC, and you’ll need a login to IRIS (through ID.me). You can download a CSV template for Forms 3921 and 3922 from IRIS.

Note: the IRS recently increased the limit on the number of records that can be included in CSV files from 100 to 250. It's possible this limit will increase again (I have no information one way or the other).

More Than 250 Returns to File

If you file more than 250 Forms 3921 or 3922, you will need to use a third-party filing solution that has the ability to submit the filing on an application-to-application basis via an API. There are various third-party providers that offer this service. It's also possible that your equity plan recordkeeping platform will offer it. 

Mandatory IRIS Filing Begins in 2027

The IRS FIRE system will be shut down on December 31, 2026. You can't submit Forms 3921 and 3922 for 2026 transactions until January 1, 2027. Thus, starting with your 2026 returns, Forms 3921, 3922 (and the full 1099 series, if you are responsible for any Form 1099-NEC or -MISC filings) must be filed using IRIS.

If you currently rely on a third-party provider to submit Forms 3921 and 3922, now is the time to start talking to them about how they will support IRIS filings and what you’ll be responsible for. Here are some questions to ask:

• Will they provide an export that includes all the data necessary to create a CSV file that can be uploaded to IRIS? Will it be in the format required by IRIS or will you need to reformat it using the IRIS template?
• Will they provide the ability to submit app-to-app filings via IRIS?
• If yes, will you need to file under your company’s TCC or will the filings be transmitted under the provider’s TCC?
• If no, will they provide an export that you can use to upload the data to another third-party solution that provides this service? Do they have any preferred partners that they recommend?

Will You Need a New Transmitter Control Code (TCC)?

Both FIRE and IRIS require a Transmitter Control Code (TCC)—but the codes are not interchangeable. The TCC identifies the entity that transmits the filings (which may or may not be the entity that is the payer listed on the returns).

If your company files its own Section 6039 returns, you may need a new IRIS-specific TCC. But this doesn’t necessarily mean that you will personally be responsible for applying for it. Each company has only one TCC for each system. Because IRIS is used for lots of other filings (e.g., 1099-NEC, 1099-MISC), your company may already have a TCC for it. The accounts payable team is typically responsible for filing Forms 1099-NEC and 1099-MISC, so I expect that they would own the company’s TCC application. IRIS is not used for Form W-2 filings (those are filed with the Social Security Administration), so your payroll team likely does not have a TCC.

More information about the TCC application process (and timeline) is available directly from this IRS tutorial. Time is of the essence here! The IRS can take up to 45 days to issue a TCC (longer if there are issues with the application), so don’t wait if you need a new one.

Can You Still File Forms 3921 and 3922 on Paper?

In nearly all cases, no.

Effective January 1, 2024, companies filing ten or more total information returns across a wide list of forms must file electronically. This includes Form W-2, 1099-series forms, and—critically—Forms 3921 and 3922.

If your company grants ISOs or offers an ESPP, you almost certainly have more than ten employees and file more than ten W-2 forms, which means electronic filing is required not only for your W-2s, but also for Forms 3921, 3922, 1099-NEC, 1099-MISC, and 1042-S.

Can You Make This Someone Else’s Problem by Outsourcing Your Section 6039 Filings?

You sure can! If you outsource your Section 6039 filings (i.e., Forms 3921 and 3922), your filing provider will take care of most or all of this for you. A filing provider can:

• Prepare electronic data files
• Submit filings
• Produce and mail employee statements
• Manage corrections

Many providers also file under their own TCC, in which case, you would not need to use your company’s TCC.

If you have more than 250 returns to file, starting in 2027 (for 2026 tax-year filings), you will have to use a provider that can file the returns via the IRIS application-to-application APIs; you will no longer be able to upload a file yourself. 

If your third-party administrator doesn’t offer Forms 3921 or 3922 filings, there are several boutique firms that offer this service.

More Resources

For more information about Section 6039 filings in general—including requirements for ISOs and ESPPs—see the NASPP’s complete guide.