SES, AES and QES: the three eIDAS electronic signature levels

eIDAS is Regulation (EU) No 910/2014, the rules governing electronic identification and trust services in the European Union. Among other things, it establishes that an electronic signature cannot be denied legal effect or admissibility as evidence merely because it is electronic (Article 25). On that basis, eIDAS distinguishes three signature levels with increasing guarantees: simple (SES), advanced (AES) and qualified (QES).

The simple electronic signature is the baseline level: any data in electronic form attached to or logically associated with other data, which the signer uses to sign. A click on "I agree", a signature drawn with the mouse, or a name typed at the foot of an email can all constitute an SES.

It is fast and low-friction, ideal for low- to moderate-risk agreements: internal approvals, authorisations, routine orders or documents between parties who already know each other. It has legal validity under eIDAS and is admissible as evidence, though in a dispute its evidential weight will depend on the supporting evidence around it.

The advanced electronic signature adds guarantees about identity and integrity. It must be uniquely linked to the signer, capable of identifying them, created using means under their sole control, and able to detect any subsequent change to the document.

In practice, AES is appropriate when the signer's identity and the document's integrity matter more: higher-value commercial contracts, agreements with new counterparties, or sectors with traceability requirements. It offers a stronger link to the signer than SES, without reaching the qualified level.

The qualified electronic signature is the highest level. It is an AES created with a qualified signature creation device and based on a qualified certificate issued by a qualified trust service provider (QTSP), which rigorously verifies the signer's identity.

Its key legal advantage: a QES has the equivalent legal effect of a handwritten signature across the EU. It is the right choice when the law demands the highest assurance or when you want the strongest possible evidential weight, for example in certain notarial, financial or public-sector acts.

The practical rule is proportionality: the higher the risk or value of the agreement, the higher the signature level. For most day-to-day commercial contracts, a well-documented SES is enough. When identity and integrity are critical, an AES is advisable. And when the law requires it or you want equivalence to a handwritten signature, QES.

An honest note about EUCLM: today we offer simple electronic signatures (SES) built into the contract flow. Advanced signatures (AES) via a qualified trust service provider are on our roadmap. We do not yet offer AES or QES natively, and we prefer to say so plainly.