IRIS CSV date format
MM/DD/YYYY, with a 4-digit year. A 2-digit year is not accepted.
Publication 5717: highlight the dates, right click, Format Cells, and on the Number tab choose Date and the MM/DD/YYYY option. "The 2-digit year format is not an accepted format."
| Written as | Accepted? |
|---|---|
| 01/31/2027 | Yes |
| 1/31/27 | No: 2-digit year |
| 2027-01-31 | No |
| 31-Jan-27 | No |
| 46418 (an Excel serial number) | No |
1099-NEC has no date column
None of the 54 columns in the tax year 2025 1099-NEC template is a date. Tax Year in column B is just the four digits. If the portal reports a date problem on a 1099-NEC file, look for a stray comma or line break that pushed values into the wrong columns, or check that you downloaded the template for the right form.
Dates matter on other forms that IRIS takes by CSV, such as 1099-S and 1098-Q.
Rules here follow the tax year 2025 guidelines, the newest the IRS has published as of 10 November 2026. Tax year 2026 guidelines were not posted yet. The IRS says the copy inside the Taxpayer Portal is the current one, so check it there before you file.
Fix the whole file at once
Drop in your blank IRIS template and your spreadsheet. Perfrow cleans every row, tells you which ones need you, and writes CSVs of at most 250 records. It runs in your browser, so names and TINs stay on your computer.
Open the 1099-NEC CSV fixerQuestions
- What date format does the IRIS CSV need?
- MM/DD/YYYY with a 4-digit year, per Publication 5717.
- Does the 1099-NEC CSV have a date field?
- No. The tax year 2025 template has a 4-digit Tax Year column and no date columns.
Other answers: All 54 columns · Required fields · Character limits · State codes · 250-record limit · Why files get rejected · Scientific notation · ZIP code format · Line breaks · Extra spaces · Periods and # · $0.00 cells · Y/N check boxes · Tax year · Error types · Headers do not match · From QuickBooks · TIN format · Key dates