Both documents describe how to hand 1099 data to the IRS. Publication 1220 does it with character positions in a text file. Publication 5718 does it with XML and a schema. The data is identical. Almost everything about how you express it is not.
- Pub 1220
- FIRE · fixed-width ASCII · retires Dec 31, 2026
- Pub 5718
- IRIS A2A · XML · required from Jan 2027
- Record length
- 750 characters per Pub 1220 record
- Pub 1220 records
- T · A · B · C · K · F
- Pub 5718 root
- IRTransmission
- Amount fields
- Codes 1-9 then A-J · I is skipped
Which publication is which
Six numbers get cited interchangeably and they are not interchangeable. Keep this straight and most IRIS documentation stops being confusing.
- Pub 1220
- FIRE fixed-width specification. The format that is going away.
- Pub 5718
- IRIS A2A specification. XML, schemas, business rules, transmission.
- Pub 5717
- IRIS Taxpayer Portal user guide. The web route, not the API.
- Pub 5719
- IRIS assurance testing package. How you get out of Test status.
- Pub 5903
- Tutorial for the IRIS Application for TCC.
- Pub 1099
- General instructions for information returns. Deadlines and penalties.
How the records map
A Pub 1220 file is a sequence of 750-character records, each opening with a type letter. Those types have IRIS equivalents, though two of them stop being your responsibility.
The C and F records are the interesting losses. In FIRE you compute and write your own issuer totals and terminate the file yourself. In IRIS both are structural, which removes a whole class of arithmetic bug and a whole class of truncated-file bug.
What actually changes
- 01
Position versus name
In Pub 1220 a field is defined by where it sits. Payee state lives at positions 488 to 489 and nothing in the file says so. In Pub 5718 the same value is a named element, so a reader can tell what it is without a spec open beside them.
- 02
Silence versus rejection
A fixed-width file with a field one character off is still a valid file. It just means something different. XML validated against a schema fails loudly instead, which is better, with one sharp caveat covered below.
- 03
Implicit versus explicit structure
Pub 1220 relies on record order: an A record opens a payer block, B records follow, a C record closes it. Break the order and meaning changes silently. XML nests the same relationship, so a payee cannot float free of a payer.
- 04
One file versus one transmission
Pub 1220 thinks in files you upload. Pub 5718 thinks in transmissions you send, each with a manifest, a receipt, and an acknowledgement you fetch back. The unit of work changes, not just the syntax.
Five traps in the conversion
These are the ones that produce a file the IRS accepts and a filing that is wrong, which is far worse than a rejection.
- 01
Amount codes are not box numbers
The single most expensive misunderstanding in the whole conversion. In a Pub 1220 B record, the money fields are keyed by payment amount code, running 1 through 9 then A through J, with I skipped to avoid confusion with the digit 1. Those codes are not the box numbers printed on the paper form. On a 1099-DIV, federal income tax withheld is box 4 on paper but amount code A in the file. Map by code and the dollars land in the right IRIS element. Map by box, and you produce a file that is structurally valid, passes schema validation, and reports the wrong numbers to the IRS.
- 02
Amounts are in cents, right-justified and zero-filled
Twelve characters per amount field, no decimal point, leading zeros. A payment of $15,000.00 is written as 000001500000. Software that writes a decimal point, left-justifies, or pads with spaces produces a file FIRE would have taken and a converter will reject.
- 03
A schema-invalid transmission cannot be replaced
This is the caveat to “XML fails loudly.” Per Publication 5718, a transmission rejected for schema validation errors still receives a ReceiptId, but you cannot use the normal replacement process. You must refile it as a new Original, with a new filing date. Validating before you transmit is not a nicety.
- 04
The schemas are not public
You can read Pub 5718 as a PDF, but the actual XSDs and business rules arrive in your e-Services mailbox and only once you hold a TCC, as the IRS schemas page states. Anyone planning to build against the format needs the TCC first.
- 05
The schema changes every tax year
A new schema version ships per tax year, and returns filed in January 2027 are tax-year 2026 returns. Tooling built and tested against the TY2025 schema is not automatically correct for the season it will actually be used in.
What to do with this
If you are buying software, the question to ask a vendor is not whether they support IRIS. It is which tax year's schema they target, and whether they map payment amounts by Pub 1220 code or by paper box number. The second question separates tools that were built from the specification from tools that were built from a screenshot of a form.
If you are building it, get the TCC first, because the schemas are gated behind it, and read Publication 5719 early so assurance testing is not a surprise. If you are staying on the free web route, Publication 5717 and our Portal limits guide are the relevant reading.
Either way, the file you feed the process decides the outcome. Our free FIRE file validator checks a Pub 1220 file against these rules in your browser, including whether each amount code is legal for its form. Nothing is uploaded.
Questions
- What is IRS Publication 1220?
- The specification for the fixed-width ASCII file format used by the FIRE system. It defines record types, field positions, and payment amount codes for 1099-series and other information returns. FIRE retires on December 31, 2026, so Pub 1220 stops being a filing format after that.
- What is IRS Publication 5718?
- The specification for IRIS Application-to-Application filing. It defines the XML transmission format, the schema validation rules, the business rules, and how transmissions and acknowledgements move between you and the IRS.
- Is Publication 5718 a replacement for Publication 1220?
- In practice yes, though they are not parallel documents. Pub 1220 describes one file layout. Pub 5718 describes a transmission protocol with a schema attached. The data is the same 1099 data; almost everything about how it is expressed changes.
- Are Pub 1220 amount codes the same as the box numbers on the form?
- No, and assuming they are is the most common conversion error. They diverge on several forms. On a 1099-DIV, federal income tax withheld is box 4 on the paper form but amount code A in the file. A converter that maps by box number produces a valid file with the money in the wrong places.
- Can I keep producing a Pub 1220 file after FIRE retires?
- You cannot file one with the IRS, but the file itself is still useful. Converters accept Pub 1220 fixed-width as input and emit the IRIS XML the IRS now expects, so an existing export from accounting or payroll software does not have to be rebuilt.
- Which publication covers the free IRIS Portal?
- Publication 5717. Pub 5718 is the A2A API specification and does not apply to Portal filing.
- How do I know whether my Pub 1220 file is correct?
- Validate it against the specification before conversion. Structure, record lengths, TIN formats, state and country codes, and whether each payment amount code is one the form actually permits. IRISfile offers a free browser-based validator that checks all of those.