IRIS CSV template and format for 1099s

The IRIS Taxpayer Portal accepts 1099s by Upload CSV with Form Data, but only in the IRS's own CSV templates^[3]. Here is where the templates and formatting rules live and what a valid file looks like.

Where to get the template

• Inside the portal. The IRS says the CSV formatting guidelines are on the Taxpayer Portal: click the Upload CSV with Form Data tile on the dashboard, then FAQ #8 on the right side of the next page has the template formatting guidelines for each form^[5].
• On IRS.gov. The IRS also posts the formatting guidelines by tax year as ZIP files. When we checked on 2026-11-14, the newest was tax year 2025 (updated 01/14/2026)^[5][6].

File rules (Publication 5717)

• At most 250 records per file, not counting the header^[3].
• One form type and one tax year per file^[3].
• Several issuers in one file only if your TCC role is transmitter^[3].
• Use the IRS-provided templates^[3]. The portal then e-files up to 100 returns at a time^[5].
• Excel reformats data such as leading zeros when you reopen a CSV; the IRS recommends Text-formatted cells and a text editor for saved files^[3].

Tax year 2026 note

The IRS added new 1099-NEC and 1099-MISC boxes for 2026^[10], so expect the TY2026 templates to have more columns than TY2025. Download the current template from your portal before you build files.

Starting from a FIRE file?

If your system writes the Publication 1220 format^[9], the converter fills these templates for you, by column name, and checks the result. See form-by-form notes.

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Sources

1. [3] IRS Publication 5717 (Rev. 9-2026), IRIS Taxpayer Portal User Guide, section 3.5
2. [5] IRS: E-file information returns with IRIS (CSV formatting guidelines by tax year)
3. [6] IRS IRIS CSV Template Formatting Guidelines, tax year 2025 (ZIP of PDFs)
4. [9] IRS Publication 1220, Specifications for Electronic Filing of Forms 1097, 1098, 1099, 3921, 3922, 5498 and W-2G
5. [10] IRS Instructions for Forms 1099-MISC and 1099-NEC (Rev. December 2026)

IRS pages checked 2026-11-14. Not affiliated with the IRS. Not tax advice.