What is knowledge-based authentication (KBA)?
Short answer
KBA verifies a person with questions drawn from their credit and public records. It is the usual identity check before a remote Form 8879 e-signature.
What it is
KBA presents the signer with multiple-choice questions generated from data an impostor is unlikely to know: previous streets lived on, a car once financed, the lender on a mortgage. Passing within a time limit counts as identity verification.
IRS Publication 1345 requires an ERO to verify the identity of a taxpayer who signs Form 8879 electronically without being present. KBA is the method most e-signature services use to meet that requirement, so it appears as an extra step before the client can sign.
Why it matters for a tax firm
KBA is where remote signing breaks for some clients: young filers, recent immigrants and people with thin credit files fail the questions because the data does not exist. Firms need a fallback, such as an in-person signature or a video identity check, before the deadline week.
Related terms
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Sources
Questions about Knowledge-based authentication
Is KBA required to e-sign Form 8879?
Identity verification is required when the signer is not in person. KBA is the common way to satisfy it; Publication 1345 describes the verification requirement rather than naming one vendor method.
What if my client fails KBA?
Have them sign in person, or use another verification method your e-signature provider offers, such as a government ID check. Do not transmit until a valid signature is in hand.
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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