What is an ETIN?
Electronic Transmitter Identification Number
Short answer
An ETIN identifies the party that transmits returns to the IRS e-file system. Most firms never need one, because their software vendor is the transmitter.
What it is
An ETIN (Electronic Transmitter Identification Number) is assigned by the IRS to a Transmitter: the party whose software actually sends return data to the IRS Modernized e-File system. Software developers and large firms that transmit directly hold ETINs; a firm that files through commercial tax software relies on the vendor's.
An ETIN starts as a test number and becomes a production number once the transmitter's software has passed the IRS Assurance Testing System for that tax year.
Why it matters for a tax firm
If your firm only uses off-the-shelf software, the ETIN is the vendor's problem. It matters when a firm or vendor builds its own filing path: no production ETIN, no live filing.
How XyloDocs handles it
XyloDocs holds its own ETINs as the transmitter for the tax software it plans for the 2027 season, so no third-party transmitter sits between the firm and the IRS. Like every transmitter, it must pass IRS testing before the production ETIN is used.
Related terms
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Sources
Questions about ETIN
Do I need an ETIN to e-file my clients' returns?
Usually not. You need an EFIN; the software company you file through holds the ETIN.
What is the difference between a test ETIN and a production ETIN?
A test ETIN is used while the software is being checked in the IRS test system. The production ETIN is issued when the software passes, and it is what live returns are sent under.
Last reviewed: October 16, 2026. This glossary explains terms; it is not legal or tax advice. Check the cited source for the current rule.
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