Simple, advanced and qualified signature: the differences

The electronic signature advanced (AES) is the most widely used level in B2B and the only one that offers a legal presumption of integrity without requiring a smart card for the signer. Alongside the simple signature (SES) and the qualified signature (QES), it makes up the three levels defined by the European eIDAS regulation. Here is how to choose the right level based on the nature of your document, its expected evidentiary value, and the level of friction acceptable to the signer.

What is the advanced electronic signature (AES)?

The advanced electronic signature is the intermediate level defined by Article 26 of the eIDAS regulation. It must meet four cumulative conditions: (1) be uniquely linked to the signer, (2) allow the signer to be identified, (3) be created using data that the signer can, with a high level of confidence, use under their sole control, (4) allow any subsequent modification of the signed document to be detected. In practice, these conditions are met through strong authentication (email + SMS OTP), a timestamped audit trail, and a cryptographic hash of the PDF.

The AES benefits from a legal presumption of integrity and origin that reverses the burden of proof in court: it is up to the party disputing the signature to prove it is false, not up to the signer to prove its validity. This is what fundamentally distinguishes the AES from the SES, where reliability is assessed case by case by the judge.

The three levels defined by eIDAS

The European eIDAS regulation (No. 910/2014) organizes electronic signatures into three levels, corresponding to increasing degrees of requirement regarding signer identification and evidentiary strength. Understanding these levels well makes it possible to choose the signature suited to each document, without over-engineering the process.

Level 1: the simple electronic signature (SES)

The simple electronic signature is the basic level. It corresponds to any expression of electronic consent: clicking "I accept", checking a box, or a scribbled initial on a touchscreen.

• Requirements: clear consent, minimal identification (email)
• Evidence: weak to moderate, varies by provider
• Use case: quotes, purchase orders, internal agreements, terms and conditions
• Signer friction: virtually none — the signer does not create an account

SES is sufficient for the vast majority of routine commercial exchanges where the risk of dispute is low. It remains legally valid, with the judge assessing the reliability of the process on a case-by-case basis.

Level 2: the advanced electronic signature (AES)

The advanced signature strengthens signer identification and establishes a unique link between the signer and the document. It relies on four criteria set out in Article 26 of eIDAS:

1. it is uniquely linked to the signer
2. it enables the signer to be identified
3. it is created using means that the signer can maintain under their sole control
4. it is linked to the document in such a way that any subsequent modification can be detected

In practice, AES relies on two-factor authentication: a unique link sent by email + an OTP code received by SMS. The final PDF includes a timestamp and a detailed audit trail.

• Use case: employment contract, lease, power of attorney, high-stakes commercial contract, NDA
• Signer friction: low — an SMS code to enter in addition to email
• Evidence: strong, rebuttable presumption of validity

Level 3: the qualified electronic signature (QES)

The qualified signature is the highest level. It relies on a qualified certificate issued by a qualified trust service provider (QTSP) listed on the trusted list of an EU member state, and on a secure signature creation device (e.g. YubiKey, smart card).

• Legal value: equivalent to a handwritten signature throughout the EU
• Use case: authentic instruments, public procurement contracts, certain notarial deeds
• Signer friction: high — face-to-face or KYC video identity verification
• Cost: significantly higher than SES/AES

For most businesses, QES is rarely necessary on a day-to-day basis. It becomes essential when required by law (legal proceedings, certain public procurement contracts) or when the contract has exceptionally high value.

Quick comparison table

How to choose the right level

The simple rule: align the level with the stakes of the document.

• If the document is disputed, what is at stake? A few hundred euros or a contract worth tens of thousands?
• Is the relationship with the signer known (long-standing customer) or unknown (first contact)?
• Does the document fall under a legal framework requiring a specific level (e.g. employment contract, lease) ?

As a general rule: SES for simple agreements, AES for anything related to HR, real estate, or finance, and QES only when required by law.

Common mistakes

• Systematically choosing QES "to be on the safe side": unnecessary friction for the signer, high cost, often over-engineered.
• Relying on SES for everything: in the event of a dispute over an employment contract, the lack of strong authentication can weaken the evidence.
• Confusing acknowledgment with signature: a receipt confirmation is not a signature.

How Certyneo helps you

Certyneo natively supports the simple (SES) and advanced (AES) levels, with double email + SMS OTP via Twilio Verify for AES. For cases requiring a QES, Certyneo interfaces with several European qualified providers (Docaposte Certigna, Universign, CertEurope) to trigger the qualified signature without switching tools.

You can set the signature level document by document based on the stakes involved — or by template if you have industrialized a process.

Discover the Certyneo electronic signature solution

FAQ

Can I mix levels within the same envelope?

Yes. A multi-document envelope can include a quote signed with SES and a contract signed with AES, for example. Each signer sees the authentication method suited to the document they need to sign.

Is the advanced signature recognized internationally?

Within the EU, yes, under the principle of mutual recognition under eIDAS. Outside the EU, recognition depends on the local legal framework — this should be checked according to the jurisdiction concerned.

Do I need a personal certificate to sign with AES?

No. AES can be obtained without a prior personal certificate thanks to double OTP. This is what makes AES very accessible, whereas QES requires a qualified certificate.

Is a qualified signature mandatory for an employment contract?

No. The employment contract accepts the advanced signature (AES), which already offers a strong presumption of validity. For more details, see electronic signature of the employment contract.

How can I verify the level of a signed document?

Open the PDF in Adobe Acrobat Reader: the signature properties display the level, the signer, and the timestamp. You can also use an online verifier.

Conclusion

Choosing the right level of electronic signature means finding the balance between evidentiary value and friction for the signer. Start simple, and step up a level when the legal stakes require it.

Try Certyneo to send, sign, and track your documents online — simply, quickly, and securely.