How a FIRE file becomes IRIS CSV
A FIRE file is a series of fixed-length 750-position records: a Transmitter "T" record, then for each issuer an "A" record, its payee "B" records and an End of Issuer "C" record, ending with an "F" record[9]. An IRIS CSV has one row per return, with one column per box, in the order of the IRS template[6].
Payer columns come from the "A" record
Positions 12-20 hold the issuer TIN, 26-27 the type of return, 53-92 and 93-132 the issuer name lines, 134-173 the address, 174-213 the city, 214-215 the state, 216-224 the ZIP and 225-239 the phone[9]. The IRIS template also asks for the payer TIN type (SSN or EIN) and a name type (B or I)[6]. The "A" record doesn't carry those, so you choose them.
Recipient columns come from the "B" record (positions 1-543 are the same for every form)
| Pub 1220 positions | FIRE field | IRIS CSV column |
|---|---|---|
| 1 | Record type (B) | - |
| 2-5 | Payment year | Tax Year |
| 6 | Corrected return indicator | not converted (correct in portal) |
| 7-10 | Name control | used to split individual names |
| 11 | Type of TIN (1 EIN, 2 SSN/ITIN/ATIN) | Recipient TIN Type |
| 12-20 | Payee TIN | Recipient Taxpayer ID Number (with dashes) |
| 21-40 | Issuer's account number for payee | Form Account Number |
| 41-44 | Issuer's office code | Office Code |
| 55-270 | Payment amounts 1-9, A-H, J (12 positions each, in cents) | form boxes, by amount code |
| 287 | Foreign country indicator | flags a foreign address |
| 288-327 | First payee name line | name fields |
| 328-367 | Second payee name line | Name Line 2 |
| 368-407 | Payee mailing address | Address Line 1 (and 2 if over 35 characters) |
| 448-487 | Payee city | City/Town |
| 488-489 | Payee state | State |
| 490-498 | Payee ZIP | ZIP |
| 723-734 | State income tax withheld | State 1 - State Tax Withheld |
| 735-746 | Local income tax withheld | State 1 - Local income tax withheld |
| 747-748 | Combined Federal/State code | CF/SF and State 1 abbreviation |
Positions from Publication 1220[9]. Column names from the IRIS CSV guidelines[6].
Amounts
FIRE amounts are whole cents in 12-position fields, with no decimal point[9]. IRIS wants dollars with at most two decimals, with no negatives and no scientific notation[6]. Convert with integer arithmetic, not floating point, so totals match to the cent.
Checks worth running before upload
- The "C" record payee count equals the number of "B" records, and each control total equals the sum of that amount code[9].
- The same totals appear in the CSV files you upload.
- TINs are 9 digits and the type matches the format[7].
- Names and addresses use only the characters IRIS allows. Addresses over 35 characters move to line 2[6].
- Individual recipients have both a first and a last name[6]. FIRE stores one name line, preferably surname first[9], so it has to be split. The name control in positions 7-10 tells you which word is the surname.
The converter does all of this and writes a report listing every change and every problem.
Get the FIRE to IRIS Converter: $49, one-time
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Sources
- [6] IRS IRIS CSV Template Formatting Guidelines, tax year 2025 (ZIP of PDFs)
- [7] IRS IRIS Working Group Questions and Answers, January 14, 2026
- [9] IRS Publication 1220, Specifications for Electronic Filing of Forms 1097, 1098, 1099, 3921, 3922, 5498 and W-2G
IRS pages checked 2026-11-14. Not affiliated with the IRS. Not tax advice.