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). For 2026 filings (the 2025 tax year), companies can choose between the long-standing FIRE system and the IRS’s newer Information Returns Intake System (IRIS). Starting in 2027, that choice goes away: all Forms 3921 and 3922 must be filed using IRIS.

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 under 100 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 IRS 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.

Which System Should You Use for 2025 Tax-Year Filings (Submitted in 2026)?

The answer to this question likely depends on several factors, including:

• Volume: The number of returns you need to file.
• Compatibility: Which system (FIRE or IRIS) your third-party recordkeeper or filing service works with.
• State Filings: Because some states do not yet accept filings made through IRIS, returns that need to be filed at the state level may need to be managed through the FIRE system.
• IRIS TCC: Whether your company has or will apply for a transmitter control code (TCC) for IRIS in time for you to submit the filings (see below for more information on TCCs).

Only a Few Returns to File

If you only have a few returns to file (e.g., a handful of ISO exercises), IRIS might be the easiest and most cost effective solution. With IRIS, you can simply manually enter the returns; you won’t need to pay for a third-party solution or deal with complicated ASCII or 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). Note that for returns filed in 2026, this solution only works for returns that don’t need to be filed at the state level (such as Forms 3921 and 3922). For filings, such as Form 1099-NEC, that must be filed at the state level, the FIRE system may still be necessary.

More Than a Few but Less Than 100 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 100 forms to file, IRIS might be a solution provided that your recordkeeper offers a file in the requisite CSV format or you can create it 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). And for returns that must be filed at the state level (i.e., not Forms 3921 and 3922), you may still need to use the FIRE system.

Having said all that, if your recordkeeper provides an ASCII file that you can easily upload to the FIRE system, that may be the easiest solution.

More Than 100 Returns to File

If you file more than 100 Forms 3921 or 3922, you are likely relying on a third-party provider to generate the files you use to submit your returns. In this case, you will be reliant on the system that your third-party provider accommodates.

• If your provider only offers a file in the ASCII format required for the FIRE system, you’ll have to use the FIRE system.
• If your provider has already upgraded their system to accommodate IRIS, you can file via IRIS. In this case, the returns will be filed on an application-to-application basis via APIs rather than uploading a file.  

Mandatory IRIS Filing Begins in 2027

The IRS will accept FIRE filings for the last time in 2026. Starting in 2027, Forms 3921, 3922, and the full 1099 series must be filed using IRIS.

If you rely on a third-party provider, now is the time to starting talking to them about they will support IRIS filings and what you’ll be responsible for. For example, will you need to file under your company’s TCC or will the filings be transmitted under the provider’s TCC?

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. 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 through the FIRE system or IRIS
• 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 100 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.

Can You Put Off Figuring Out IRIS for another Year?

If you currently have a solution that enables you to submit your 2025 Section 6039 returns via the FIRE system and you are happy with it, you absolutely can wait until you have to submit your 2026 tax-year returns to figure this out. But I don’t recommend leaving it until the last minute.

More Resources

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