eIDAS Explained: SES vs AdES vs QES

The eIDAS Regulation (Regulation (EU) No 910/2014, as amended by Regulation (EU) 2024/1183) is the law that governs electronic signatures across all 27 EU member states. It defines three tiers of electronic signature, each with a different level of identity assurance and legal weight.

Choosing the right tier matters: too low and a high-stakes document may not hold up; too high and you add cost and friction the transaction never needed. For the large majority of commercial agreements, the simplest tier is enough.

Simple Electronic Signature (SES)

A Simple Electronic Signature is, in the words of eIDAS Article 3(10), “data in electronic form which is attached to or logically associated with other data in electronic form and which is used by the signatory to sign.”

That broad definition covers a typed name, a drawn signature, or clicking “I agree.” An SES carries the protection of Article 25(1): it cannot be denied legal effect or rejected as evidence solely because it is electronic.

• Identity verification: none required by the standard itself (the platform may still capture email, IP, and timestamps).
• Tamper-evidence: not required by the tier, though good platforms add it anyway.
• Best for: sales agreements, NDAs, statements of work, HR paperwork, order forms — the everyday B2B and B2C contracts that make up most signing.

Advanced Electronic Signature (AdES)

An Advanced Electronic Signature must meet four requirements set out in eIDAS Article 26:

1. It is uniquely linked to the signatory.
2. It is capable of identifying the signatory.
3. It is created using data the signatory can use under their sole control with a high level of confidence.
4. It is linked to the signed data so that any later change is detectable.

In practice this usually means identity verification plus a cryptographic, certificate-based signature that seals the document.

• Identity verification: required.
• Tamper-evidence: required.
• Best for: higher-value or higher-risk agreements — significant financial contracts, some employment contracts, regulated-industry documents.

Qualified Electronic Signature (QES)

A Qualified Electronic Signature is the highest tier. Under Article 3(12) it is an AdES that is additionally:

• created by a Qualified Signature Creation Device (QSCD) — certified secure hardware or a qualified remote service, and
• based on a qualified certificate issued by an EU-accredited Qualified Trust Service Provider, which verifies the signer’s identity (often in person or by equivalent means).

QES is the only tier that, under Article 25(2), has “the equivalent legal effect of a handwritten signature” automatically across the entire EU. A QES issued in one member state is recognised in all others (Article 25(3)).

• Identity verification: strong, by an accredited provider.
• Tamper-evidence: required, hardware-backed.
• Best for: the specific transactions national law reserves for it — certain real-estate transfers, notarial acts, some corporate filings, and dealings where a member state mandates a handwritten-equivalent signature.

SES vs AdES vs QES at a glance

	SES	AdES	QES
Identity verified	No (optional)	Yes	Yes, by accredited provider
Tamper-evidence	Not required	Required	Required, hardware-backed
Admissible as evidence	Yes (Art. 25(1))	Yes	Yes
Auto-equal to handwriting EU-wide	No	No	Yes (Art. 25(2))
Typical cost & friction	Lowest	Medium	Highest
Best for	Most business contracts	High-value agreements	Documents the law reserves for it

Which level do you actually need?

For the overwhelming majority of commercial transactions, an SES is sufficient and admissible. Article 25(1) protects it, and a strong audit trail gives it real evidentiary weight. Reach for AdES or QES only when a counterparty, a regulator, or a member state’s national law specifically requires that higher tier — most often for real estate, notarial deeds, or certain formal filings.

If you are unsure whether a specific document requires QES in a specific country, that is a question for a qualified local lawyer — the requirement comes from national law, not from eIDAS itself.

What Signatura supports

Signatura provides Simple Electronic Signatures (SES), with a complete audit trail and a SHA-256 tamper-evident seal on every completed document. SES covers the vast majority of B2B and commercial agreements.

Signatura does not currently offer AdES or QES. If your transaction specifically requires a Qualified Electronic Signature under a member state’s law — for example a real-estate transfer or a notarial act — you’ll need a Qualified Trust Service Provider for that document. We’d rather tell you that plainly than overstate what we do. You can read more on our security page, and our take on overall validity in Are electronic signatures legally binding?

Frequently asked questions

Is an SES legally valid in the EU?

Yes. Under eIDAS Article 25(1), a simple electronic signature cannot be denied legal effect or rejected as evidence solely for being electronic. It is suitable for most commercial contracts.

Do I need a QES for a normal business contract?

Almost never. QES is reserved for specific transactions that national law requires it for, such as certain real-estate or notarial documents. A standard sales agreement or NDA does not need one.

What’s the difference between AdES and QES?

A QES is an AdES with two additions: it is created on a certified secure device (a QSCD) and uses a qualified certificate from an accredited provider. That combination is what gives QES automatic handwritten-equivalent status across the EU.

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Sources: Regulation (EU) No 910/2014 (eIDAS), EUR-Lex — see Articles 3, 25, and 26; Regulation (EU) 2024/1183 (eIDAS 2.0), EUR-Lex.