Two-Factor Signing: How 2FA Works for E-Signatures

Two-factor signing means a signer must prove who they are with two different kinds of proof before they can open or sign a document. Typically that is access to the email link (something they have) plus a one-time code, a password, or a face match. It does not make a signature legal by itself, but it gives you much stronger evidence of who signed. This guide explains how it works, which methods fit which documents, and how to roll it out.

TL;DR

• Two-factor signing requires two authenticators from different categories: something the signer knows, has, or is. Two passwords do not count.
• U.S. law (ESIGN) does not require 2FA for most signatures, but some regulated records, such as those under FDA and ATF rules, do require two identification components.
• Authentication confirms the same person is returning. Identity verification, such as a government ID check with a face match, confirms who that person really is. High-value documents often need both.
• SMS codes are better than a password alone, but NIST flags interception risks. Pick the method based on what is at stake in the document.
• Plan recovery in advance: signers who lose a phone or inbox need a defined path back in.

Table of Contents

• What two-factor signing means
• How 2FA works in an e-signing process
• Does 2FA make a signature legal?
• Choosing the right method for the document
• Setting up two-factor signing
• What happens when a signer loses their phone or inbox
• Perspective
• Put two-factor signing in your workflow with BeeSign
• Common mistakes to avoid
• FAQ
• Sources

What two-factor signing means

Two-factor authentication (2FA) requires two authenticators from two different categories. The National Association of Secretaries of State describes the three categories as something you know, something you have, and something you are. Two items from the same category, such as a password and a security question, are not multi-factor.

In e-signing, the categories look like this:

So “two-factor signing” is shorthand for a signing flow where opening or completing the signature takes two of these. A signing link sent to an email address is one factor, if you treat inbox access as something the signer has. Adding a code texted to a phone, or a selfie matched to an ID, makes it two.

Authentication is not identity proofing

The two ideas are often blurred. NASS notes that authentication and identity proofing are different processes: authentication shows that the same account is coming back, while proofing establishes that the account belongs to a specific real person.

That difference matters for signing. A texted code proves the person holds a phone number. It does not prove the phone belongs to the person named in the contract. For that, you add identity verification, for example capturing a government ID and matching the signer’s face to it.

How 2FA works in an e-signing process

The exact screens vary by platform, but the sequence is consistent:

1. The sender prepares the document. They add the signer’s name and email and choose an extra authentication step for that signer, such as a code by text message or an ID check.
2. The signer receives an email with a secure link. Opening it is the first factor: it shows control of that inbox.
3. The signer is asked for a second proof. This might be a one-time code sent by SMS, a code from an authenticator app, a password the sender gave them separately, or a selfie and ID capture.
4. The signer enters the proof and gains access. A wrong entry is rejected, and most systems limit the number of attempts.
5. The signer reviews and signs. The platform records the event, including which authentication step was passed, in the audit trail.

That last step is the practical payoff. When a signature is questioned later, an audit trail showing that the signer passed two checks is far more persuasive than one showing only that a link was opened. For background on what the signing record itself contains, see our explainer on how an electronic signature works.

The password method

The simplest second factor is a password the sender sets. Some platforms work this way: the sender creates a password in the application and must communicate it to the recipient through an external channel, meaning not in the same email as the link. The separate channel is the point. If both the link and the password sit in one inbox, an attacker who reads that inbox gets both. Sharing the password by phone call or a different messaging app keeps the factors apart, and the same logic of treating credentials as separate from the data they protect runs through good security practice generally.

The code method

A one-time code sent by text or generated in an app is the most familiar approach. It suits routine agreements: vendor contracts, onboarding paperwork, lease addenda. Signers already know how to use it, and it takes seconds.

The identity verification method

For documents where you must know exactly who signed, add a check that ties the person to an official identity. BeeSign’s identity verification supports government ID capture and biometric face matching as part of the signing workflow, so the identity step and the signature live in one record instead of two systems.

Does 2FA make a signature legal?

No, and it helps to be exact about this. Under the ESIGN Act, a signature or record cannot be denied legal effect, validity, or enforceability solely because it is electronic. The law does not tell you to add a second factor to reach that baseline. What makes a signature valid is intent to sign, consent to do business electronically, association of the signature with the record, and record retention. We cover these in what makes an eSignature valid and in our guide on whether electronic signatures are legally binding.

What 2FA adds is evidence. If a signer later says they never signed, you need to show it was them. Two verified factors, logged in an audit trail, are strong proof of that. That is a practical benefit in a dispute, not a legal threshold.

Consumer consent still applies

When the signer is a consumer, a second factor does not replace the consent step. ESIGN requires that a consumer affirmatively consent electronically to receive records in electronic form, after a clear and conspicuous disclosure of their rights, including the right to receive paper copies. If you handle consumer documents, put the disclosure and consent screen before the authentication step, and keep the record. A useful overview of how these consent, disclosure and retention rules sit alongside automated document handling can help teams that process high volumes. Our eSignature compliance requirements guide walks through the full list.

Where rules do require two components

Some regulated records do spell out a two-component requirement:

• FDA electronic records. Under 21 CFR § 11.200, non-biometric electronic signatures must use at least two distinct identification components. During one continuous controlled-access session, the first signing uses all components and later signings need at least one component only the user holds. Signings outside that session require all components each time.
• Select agents and toxins. Under 27 CFR § 73.11, a non-biometric signature must use at least two distinct identification components, such as an identification code and password, use both when signing, and be usable only by the authorized user.
• State e-signature policies. The California Department of General Services’ security procedures say SMS may be used for a high-dollar amount or type of contract, which shows how public agencies tie the strength of the check to the stakes.
• Remote online notarization. The National Notary Association explains that remote notarization commonly uses multi-factor authentication, including credential analysis and dynamic knowledge-based authentication, and that requirements vary by state.

If your documents fall under one of these regimes, confirm the specifics with your compliance lead or counsel. For everyday business contracts, 2FA is a risk decision, not a legal requirement.

Choosing the right method for the document

Match the strength of the check to the damage a forged signature could do. A useful way to decide is to look at the impact if the wrong person signs. The same assurance-by-impact logic appears in payment authentication practice, and in government guidance on electronic signatures, which recommends assessing assurance levels based on the impact of threats to the transaction.

Treat this table as a starting point, not a rule. Your industry, your insurer and your counsel may set a higher bar.

Know the weak points of SMS

Text message codes are popular because they are easy. They are also not the strongest option. NIST’s discussion of its digital identity guidance says SMS is more protective than a password alone but less secure than device authentication mechanisms, and it identifies VoIP delivery and SMS interception or redirection as risks. NIST has cautioned since at least 2016 that internet-based phone services can be used to intercept codes.

The stronger alternative is a phishing-resistant authenticator. Per NIST’s 2024 small business guidance, authenticators built on FIDO standards and the W3C Web Authentication API remove manual code entry and bind authentication to the specific website or domain, which blocks the most common phishing tricks. NIST also says not every transaction needs this, but organizations should enforce or at least offer it for applications with sensitive information, such as health information or personally identifiable information.

A practical reading for a signing workflow:

• Use code-based 2FA for routine business documents.
• For high-value or sensitive documents, add identity verification and prefer authenticators tied to a device.
• Do not let the second factor travel in the same channel as the first.

Setting up two-factor signing

Whatever platform you use, work through this checklist before you send your first protected document.

1. Classify your document types. List what you send most often and mark each as low, moderate or high impact.
2. Pick a default check per class. For example: code for moderate, ID check for high.
3. Collect the right contact data up front. A code by text needs a verified mobile number. Confirm it with the signer through a separate channel, not by guessing.
4. Put consent first. For consumer signers, show the ESIGN disclosure and capture consent before authentication.
5. Build templates. Save each authentication setting inside a reusable template so staff do not choose it by hand each time.
6. Test as a signer. Send a test document to yourself on a phone, and note the screens, wait times and error messages.
7. Write a recovery procedure. See the next section.
8. Check the audit trail. Confirm it records the authentication step, not just the signature.

If you automate sending from your own app or CRM, the same settings can be applied through an API so the right check is applied every time without manual choices.

What happens when a signer loses their phone or inbox

Authentication fails in real life more than people expect. A signer changes numbers, gets a new phone, or cannot reach an old inbox, and the contract stalls. Decide the recovery path before it happens.

Good practice from large identity systems is a useful model:

• Login.gov advises users to regain access to the original phone number if possible, or sign in with another method already set up, and to add more than one method in advance.
• ID.me’s recovery process has a user who cannot complete MFA start recovery, confirm ownership through a live selfie, video call, email or personal-information checks, or an identity document, then set up a new method.

For a business sending contracts, translate that into three rules:

1. Do not reroute a code to a new number on request alone. An attacker will ask the same thing. Verify the person by another route first, such as a call to a known number or an ID check.
2. Offer a second method at the start where the signer can choose, such as email plus an alternate phone.
3. Log the change. Keep a note of who approved the new contact detail and how.

Perspective

We see two-factor signing as one layer in a signing workflow, not a separate product bolted on at the end. A code stops a stranger from opening a link. It does not tell you that the person behind the phone is the person named in the agreement. That is why we build identity verification, with government ID capture and biometric face matching, into the same platform as signing, templates and the audit trail. One record, one place to look when someone asks who signed and how.

We also think where the data lives matters as much as how the signer logs in. With white-label and bring-your-own-cloud storage, you can run signing under your own brand and domain and keep documents in your own infrastructure. For teams in healthcare, education, HR and real estate, that is often what makes a security review pass.

Our advice: set your authentication level by document type, save it in templates, and let the workflow apply it every time. People make fewer mistakes when they are not asked to decide on each send.

Mustafa Abusharkh

Put two-factor signing in your workflow with BeeSign

BeeSign brings signing, reusable templates, approvals, identity verification and complete audit trails into one platform, with a REST API for automation. Pricing is flat-rate, without per-envelope fees, so adding a check to more documents does not raise your bill per send. The Individual plan is $9.99 per month after a 7-day free trial, and Enterprise and custom integrations are quoted individually. See the plans on our pricing page or explore electronic signatures.

If you need the signing service under your own name, with a custom domain and storage you control, look at our white-label and BYOC options.

Common mistakes to avoid

• Sending the link and the password together. That collapses two factors into one.
• Using security questions as a second factor. A question is another thing the signer knows, so it does not add a new category.
• Asking for strong checks on every document. Friction drives signers away. Reserve heavier checks for higher-impact documents.
• Skipping the record. If the audit trail does not show which check was passed, you lose most of the evidentiary value.
• Forgetting that the law has other requirements. ESIGN preserves other legal requirements, so a second factor never excuses a missing disclosure or a document type that must be on paper. Our post on whether legal documents can be signed electronically covers the exceptions, and the guide to choosing ESIGN-compliant software lists what to look for in a platform.

FAQ

Is two-factor signing the same as two-factor authentication?

They are closely related. Two-factor authentication is the general method of requiring two proofs of identity. Two-factor signing applies it to the moment a person opens or signs a document, so that both proofs are logged alongside the signature.

Does a signature need 2FA to be legally binding in the U.S.?

For most business and consumer documents, no. ESIGN says a signature cannot be denied effect only because it is electronic. Some regulated records, such as those under 21 CFR Part 11, do require at least two identification components, so check the rules for your industry.

Is an SMS code good enough?

It is a real improvement over a password alone and suits routine documents. NIST notes it is less secure than device-based authenticators because codes can be intercepted or redirected. For sensitive records, add an ID check or use a phishing-resistant method.

Does a face match count as a second factor?

Yes. A face match is something the signer is. Matched against a government ID, it also helps establish who the signer is, not only that the same person came back, which is the difference between authentication and identity proofing.

What if the signer cannot receive the code?

Do not simply change the phone number on request. Confirm the signer through another route, such as a call to a known number or an ID check, then update the contact detail and record the change.

Sources

• ISSUE BRIEFING: Digital Identity (NASS, 2022)
• 15 U.S. Code § 7001, General rule of validity
• ESIGN Act consumer consent report (FTC)
• 21 CFR § 11.200, Electronic signature components and controls
• 27 CFR § 73.11, Required components of electronic signatures
• California DGS E-Signature Security Procedures
• Understanding Different Methods of Notarization (NNA)
• Adobe Sign Recipient Authentication Methods (Texas A&M)
• NIST: Questions and buzz surrounding draft SP 800-63-3
• NIST small business identity and access management guidance (2024)
• NIST: Multi-Factor Authentication
• Login.gov: How to sign in if you lost your phone or personal key
• ID.me MFA recovery steps
• 3D Secure authentication guide
• Document automation and handling
• Security practices for protecting data

Recommended

• OTP Verified Electronic Signature Explained
• Signer Biometrics: When Identity Needs More Proof
• Document Signing With Identity Verification
• How to Verify Signer Identity Online