The three types of electronic signatures: SES, AES, QES — explained.

Under eIDAS, three tiers of electronic signature exist — and the gap between them is the difference between signing something that's actually binding and signing something that only looks binding. Get the tier wrong and you discover it at the worst possible moment: in front of a judge.

SES is what most people imagine when they picture a digital signature. Someone clicks "sign", their name appears as proof they did it, and a timestamp says when. That's it.

No identity verification. No special certificate. No encryption. No tamper protection. You could forge an SES by copying another person's signature image. You could alter a document after signing and the SES would still sit there, perfectly happy. Technically, SES is barely more than metadata attached to a file.

Here's the thing: SES is technically legally valid under eIDAS. Courts will look at it. But if someone later claims they never signed, you're fighting an uphill battle. SES works fine for internal approvals where everyone trusts everyone else. The moment external parties or real risk are involved, SES is a liability dressed up as a solution.

AES is where most business contracts should live. It requires qualified digital certificates — a certificate authority verifies identity before issuing one. It doesn't require a government ID scan (that's QES), but it does require real verification, often a phone check combined with identity checks through other channels.

Once the certificate is in place, an AES signature becomes mathematically linked to the document. You can't alter it after signing without the signature becoming invalid. Change even one character and the whole thing breaks. Commercial contracts, NDAs, employment agreements, leasing, services — AES covers them all.

QES is the heavyweight division. It requires a qualified certificate issued by a government-approved trust service provider, and your identity is verified in person using official documents — passport, national ID card, or equivalent. It costs more and takes longer because it's actually rigorous.

The legal difference is decisive: under eIDAS, a QES has exactly the same legal weight as a handwritten signature. Full stop. The burden of proof flips. If someone disputes a QES, they must prove it was forged. You don't have to prove it was legitimate. This matters for M&A, employment contracts with real severance exposure, credit agreements, medical records, and sensitive legal deeds.

The cost delta between AES and QES is usually smaller than people expect — often just a few euros per signature. The difference in legal protection is enormous.

Ask these questions in order:

1. 1
   Is this internal?

   Use SES. No external parties means signatures are just workflow tracking.

2. 2
   Is this a standard commercial contract with an external party?

   Move to AES. NDAs, service terms, leasing, employment — AES is the standard for a reason.

3. 3
   Is significant money, legal complexity, or regulation involved?

   Use QES. M&A. Credit agreements. Healthcare. Real estate. Employment with real severance exposure.

4. 4
   Is your counterparty specifying a tier?

   Use what they ask for. Defer to contract terms and industry standards.

Most businesses need AES as their baseline. It's the thinking person's choice: real security without the overhead of full government ID verification, legal cover on normal commercial agreements, no unnecessary complexity.

Some businesses occasionally need QES for high-value contracts. Build that into your workflow. Know when you need it.

And SES? Unless you're using it internally or for the most trivial sign-offs, you're taking an unnecessary risk. The legal cover isn't there when things go wrong.