SES, AES or QES? Choosing the Right Electronic Signature Under eIDAS

Three levels of electronic signature

The EU's eIDAS Regulation defines three levels of electronic signatures, and they mean the same thing in every member state:

• SES — simple electronic signature: Any data in electronic form attached to other data and used to sign. That covers everything from a typed name at the bottom of an email to a drawn signature on a screen or clicking "Accept and sign" in a signing tool.
• AES — advanced electronic signature: A signature uniquely linked to the signer, capable of identifying them, created using means under the signer's sole control, and linked to the document so that any subsequent change is detectable. In practice this usually means signing tied to a verified electronic identity — in the Nordics via national eID schemes such as Denmark's MitID.
• QES — qualified electronic signature: An AES created with a qualified signature creation device and based on a qualified certificate from an approved trust service provider. Under eIDAS, a QES has the same legal effect as a handwritten signature throughout the EU.

The key point: all three are legally valid

Here is what many vendors do not say out loud: eIDAS states that an electronic signature may not be denied legal effect solely because it is electronic or not qualified. And in most EU jurisdictions contract law is built on freedom of form — an agreement is binding whether concluded orally, on paper or with an SES.

The difference between the levels is therefore not primarily validity, but evidential weight: how easily can you later prove who signed and that the document has not changed? An SES can be disputed with "that click was not me". An AES backed by a verified eID is far harder to walk away from, because a trusted third party verified the identity and the document is cryptographically sealed.

When is SES enough?

SES works fine for documents where the risk of a signature dispute is low, and where other evidence exists anyway (email trails, payments, deliveries):

• Quotes and order confirmations: Acceptance is usually confirmed by the subsequent trade anyway.
• Ordinary B2B agreements: Cooperation agreements, NDAs and delivery agreements between professional parties, where neither side has a real interest in disputing its own signature.
• Internal approvals: Policies, staff handbooks, expense approvals, risk assessment action plans.

A good SES solution also logs more than people think: timestamps, email verification, IP address and a sealed audit trail. That is a solid evidence package even without an eID.

When should you use AES?

Choose AES when the document has high value, a long lifetime, or when the counterparty is a private individual whose identity you do not already know:

1. Employment contracts: The contract governs the relationship for years, and disputes typically surface only once there is a conflict — exactly when you want identity proven beyond doubt. In several EU countries, eID-backed AES is the de facto standard for employment contracts.
2. Agreements with private individuals: Leases, consumer contracts, consent declarations.
3. High-stakes or form-sensitive documents: Loan notes, guarantees, executive contracts, shareholder agreements.

Note that a small number of document types carry statutory form requirements or dedicated public registration systems — property registration is a common example. If a specific document type has a statutory form requirement, check with an adviser.

What about QES?

QES matters when the law explicitly requires a "qualified electronic signature" — some member states require it for specific documents such as certain consumer credit agreements or filings — or when you sign towards foreign parties or authorities demanding the highest level. In everyday B2B life the need is rare: AES covers almost every situation where SES does not suffice. Also note that an eID-backed signature is by default an AES; QES additionally requires a qualified certificate from a qualified trust service provider.

A simple rule of thumb

• Low risk, known counterparty, short lifetime: SES
• High value, private individuals, employment, long lifetime: AES with eID
• Explicit statutory requirement for a qualified signature or heavyweight cross-border documents: QES

And whatever the level: make sure the solution seals the document after signing and stores an audit trail — that is what decides the evidential weight the day it matters.

How Verkta helps

With Verkta's e-signature you send documents for signature in under a minute and choose the level per document: SES for quotes and internal approvals, eID-backed signing for employment contracts and other important agreements. Every document is cryptographically sealed and stored with a full audit trail. Try it free for 14 days.