Signatures (Advanced): Knowledge-Based Authentication (KBA)


Note: KBA is available to U.S. clients and firms only.

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Knowledge-based authentication (KBA) is required for IRS Form 8879. TaxDome fully meets IRS requirements at a cost of $1 per signature.

Covered here:


KBA is used to verify the identity of a taxpayer in order to get IRS-compliant electronic signatures. Clients are verified through a combination of ID-document and consumer-data verification.


Tip: Find out more about KBA and pricing comparisons on our blog.

Here’s how it works:

1. First, you need to add funds to your firm’s balance. Each signature authentication per document costs $1.

2. Second, upload the document that needs to be signed, request the signatures, then toggle on Require KBA.

3. When signing, your client will be asked to verify their social security number and answer five questions randomly generated from their public records. These are usually multiple-choice questions—such as the name of their mortgage lender, type of car, a former address or previous phone number. It’s not a credit check but a way to digitally verify their identity.

4. The client gets only two attempts to answer the KBA questions. They need to answer at least three out of five correctly during either attempt.

You'll receive a notification when a user passes or fails a KBA.

Adding Funds to Your Firm’s Balance

Each KBA attempt costs $1 per signer. Depending on your needs, you have the option to add $20, $50, $100, $250, $500 or $1000 to your firm’s balance. Go to Settings, navigate to the Firm Balance tab, select the amount, then click BUY. This can be done by a firm owner, Admin or any employee who has access rights to charge firm balance.

You can always view your KBA usage stats by clicking the Audit trail link at the top right of the Firm Balance page.

Adding KBA to a Signature Request

To request a signature with KBA:

1. Upload the document to the Firm docs shared with client folder, click on the three dots to the far right of the document’s name, then click Request Signature in the pull-down menu.

2. Toggle on Require KBA, then add the required signature fields.

Keep in mind:

  • A document can contain as many signature fields as needed. Pricing is per document. If you merge documents (state, federal, etc.) into one file, KBA costs $1 per signer.
  • When requesting a signature with KBA for a client account that has two or more email addresses in their linked contacts, indicate which user needs to sign the document by selecting their email address in the Clients drop-down.
  • If you add fields for two or more users, each signer’s verification attempt will cost $1. For example, two spouses will be charged a minimum of $2; if they fail to pass the KBA, they will be able to attempt one more time for a maximum charge of $4 (2 signers x 2 attempts x $1).
  • If your firm balance is 0, or you have pending KBA signatures that are equal to your balance, you’ll be prompted to add funds.
  • If one of the signers fails the KBA, you will need to upload the prepared document again and request a signature for it one more time.
  • This will not work for ITINs, so make sure that your clients have SSNs before enabling KBA.

Can a Client Use an ITIN instead of an SSN for KBA?

No. An Individual Taxpayer Identification Number (ITIN) is issued to an individual for taxation purposes only. ITINs are not meant to be used as identification for obtaining credit. Credit systems won’t recognize them as anything other than an incorrect SSN, so they cannot be used for KBA.

Is Either a Soft or Hard Credit Check Performed During the KBA Check?

No. During KBA no credit is verified, so neither hard nor soft credit check is done.

What to Do if a Client Fails KBA

A client gets two attempts to answer KBA questions. If they fail answering correctly both times, you’ll receive a notification, and the KBA failure will also be noted in the document’s audit trail.

You can use either of these workarounds:

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