An EFIN (Electronic Filing Identification Number) is the number the IRS assigns to a tax professional or firm after it applies for and passes the e-file suitability check, authorizing that person or firm to electronically file returns as an Authorized IRS e-file Provider.
Why it matters to a preparer
Without an EFIN tied to your firm, you can't transmit returns through IRS e-file. It's also easy to confuse with a PTIN: a PTIN identifies you as the preparer and is renewed every year, while an EFIN identifies the firm or Electronic Return Originator (ERO) authorized to transmit returns and isn't on that same annual renewal cycle. A solo preparer who both prepares and e-files needs both numbers, and neither substitutes for the other.
E-filing itself is mandatory for most paid preparers once they're above a low threshold of returns filed per year, which is why almost every real practice ends up needing an EFIN sooner or later — it stops being optional the moment your client list grows past a hobby.
How it works
You apply for an EFIN through the IRS's e-file application process, described in IRS Publication 3112, "IRS e-file Application and Participation": create an IRS e-Services account, submit the application with details about your firm and its principals, and go through the suitability check. Publication 3112 says suitability checks may include a tax compliance check, a check for prior non-compliance with IRS e-file requirements, and a criminal background check; the IRS's e-file provider page also mentions a credit check. Principals and Responsible Officials are generally fingerprinted through an IRS-authorized vendor as part of that suitability check, unless they provide professional credentials. Because the review can take weeks, applying well before the season you plan to file in — not in January — is what keeps it from becoming a bottleneck.
Once issued, the EFIN doesn't need to be renewed annually the way a PTIN does, but you're expected to keep your e-file application information current and to periodically check your EFIN's status and filing volume through IRS e-Services, since a number that's inactive or shows unexpected volume is worth investigating right away. An EFIN also isn't transferable — it belongs to the approved firm and application, not to a person who can carry it to a new firm. For the full step-by-step process, see our EFIN guide and e-file setup guide.