Difference Between SES, AES, and QES – Simple, Advanced, and Qualified Electronic Signatures
SES, AES, and QES represent the three levels of electronic signatures recognized under Swiss and European law. SES is the simplest form, AES provides enhanced security, and QES is the highest level with legal equivalence to a handwritten signature. Which signature you need depends on statutory requirements and the intended use case.
What is SES (Simple Electronic Signature)?
The Simple Electronic Signature (SES) is the most basic form of digital signature. It encompasses any electronic data used for signing purposes – such as checking a box, scanning a handwritten signature, or sending a signed email.
SES does not provide unique identification of the signer and cannot reliably detect post-signature modifications. While widely used in practice, it has limited evidentiary value in court. For internal approvals, simple confirmations, or documentation without high legal requirements, SES is often sufficient.
When is SES sufficient?
- Internal documentation and approvals
- Confirmations without statutory requirements
- Email-based agreements in daily use
- Surveys and feedback forms
What is AES (Advanced Electronic Signature)?
The Advanced Electronic Signature (AES) meets higher requirements than SES. It is uniquely linked to the signatory and can identify that person. Any modifications to the document after signing are detectable.
AES is typically enabled through a personal certificate bound to a natural person. In Switzerland, ZertES (the Federal Act on Certification Services in the Area of Electronic Signatures and Other Applications of Digital Certificates) governs the requirements. In the EU, the eIDAS Regulation is the applicable framework.
Advantages of AES over SES
- Unique attribution to a specific person
- Detection of post-signature modifications
- Higher evidentiary value in disputes
- Suitable for medium-risk contracts
Typical use cases for AES
- Servitude agreements and arrangements
- Employment confirmations and order confirmations
- Confidential business documents
- B2B contracts
What is QES (Qualified Electronic Signature)?
The Qualified Electronic Signature (QES) is the highest tier of electronic signature. It meets the strictest requirements and — when combined with a qualified timestamp — is legally equivalent to a handwritten signature under Swiss law (CO Art. 14 para. 2bis). QES requires a qualified certificate issued by a recognized certification service provider.
QES requires strong authentication of the signatory, for example via video identification or electronic ID (eID). Modifications to the document are traceable through an integrated seal. QES is regulated in Switzerland under ZertES and in the EU under the eIDAS Regulation.
When is QES sufficient — and when is it not?
In Switzerland, a straightforward principle applies: contracts without statutory form requirements can be concluded in any form. Where the law requires written form, QES serves as an equivalent alternative to a handwritten signature on paper. Where the law explicitly requires the signer's own hand, even QES is insufficient.
QES as equivalent to handwritten signature
QES — together with a qualified timestamp — is legally equivalent to a handwritten signature and can be used wherever the law requires written form. Typical examples:
- Consumer credit agreements (CCA Art. 9) and temporary employment contracts (statutory written form requirement)
- Corporate resolutions and powers of attorney in business transactions
Paper is mandatory — QES is not enough
Certain legal acts explicitly require the signer's own hand or even handwritten drafting. In these cases, only paper will do:
- Holographic wills — must be handwritten in full and signed by hand (CC Art. 505)
- Surety declarations — require the surety's own handwritten signature and handwritten specification of the maximum liability amount (CO Art. 493)
Real estate transactions: Not just a signature question
Real estate purchase agreements in Switzerland mandatorily require notarial authentication (CO Art. 216). The signature on the purchase contract can be electronic, but the notarial process is required regardless. QES does not replace notarial authentication.
Employment contracts: No form requirement
Standard employment contracts in Switzerland are subject to no form requirement (CO Art. 320) — they can even be concluded orally or by implied agreement. A signature is not legally required but can improve evidentiary standing. Exceptions exist for apprenticeship contracts (Art. 344a CO), which require written form.
Practical rule of thumb
| Requirement | Signature type |
|---|---|
| No form requirement (e.g. employment contract) | Any form (including electronic without signature) |
| Statutory written form (e.g. consumer credit) | Handwritten or QES with qualified timestamp |
| Own hand prescribed (will, surety) | Paper with handwritten signature only |
| Notarial authentication (real estate) | Notary + any signature form |
SES vs. QES Compared
| Criteria | SES | AES | QES |
|---|---|---|---|
| Signer Identification | No unique attribution | Uniquely attributed | Uniquely attributed and verified |
| Modification Detection | Not guaranteed | Guaranteed | Guaranteed and certified |
| Evidentiary Value | Limited | Medium to high | Very high (equivalent to handwritten) |
| Legal Basis CH | No specific regulation | ZertES | ZertES |
| Legal Basis EU | eIDAS | eIDAS | eIDAS |
| Typical Use | Internal, non-critical documents | Medium-value contracts | Statutory requirements, sensitive documents |
| Cost | Very low | Medium | Higher (qualified certificate required) |
Decision Guide: Which Signature Do I Need?
Step 1: Check Statutory Requirements
Determine whether your document is subject to statutory form requirements. For real estate transactions, notarial authentication is mandatory; for wills, even QES is insufficient — only paper works. For consumer credit agreements or powers of attorney, QES or a handwritten signature will suffice.
Step 2: Assess Risk and Document Value
For documents with high dispute potential or significant value, AES or QES is recommended to ensure strong evidentiary standing in case of conflict.
Step 3: Consider Identification Effort
QES requires greater effort for signer identification (e.g., video identification). If this is not required by law or circumstance, AES may be a practical alternative.
Quick Reference
- SES: For internal, non-critical documents
- AES: For contracts that do not legally require QES but need elevated security
- QES: For documents with statutory written form requirements or maximum evidentiary weight
Frequently Asked Questions (FAQ)
What is SES (Simple Electronic Signature)?
The Simple Electronic Signature (SES) is the most basic form of digital signature. It does not provide unique identification of the signatory and has limited evidentiary value. Examples include scanned signatures or accepting terms via a checkbox.
What is AES (Advanced Electronic Signature)?
The Advanced Electronic Signature (AES) is uniquely linked to the signatory and can detect modifications to the document after signing. It offers higher evidentiary value than SES and is suitable for many types of business contracts.
What is QES (Qualified Electronic Signature)?
The Qualified Electronic Signature (QES) is the highest tier of electronic signature. When combined with a qualified timestamp, it is legally equivalent to a handwritten signature (CO Art. 14 para. 2bis). It requires a qualified certificate and strong authentication of the signatory.
What is the difference between SES and QES?
The main difference lies in evidentiary value and legal requirements. While SES has only limited evidentiary value, QES is legally equivalent to a handwritten signature. QES requires a qualified certificate and verifiable identification of the signatory.
When do I need QES instead of AES?
You need QES when the law requires written form — for example, for consumer credit agreements (CCA Art. 9) or certain powers of attorney. QES is also the right choice when you require the highest possible evidentiary value in case of dispute. For wills and surety declarations, a handwritten signature on paper is required by law — QES is not sufficient in those cases.
Is electronic signature valid in Switzerland?
Yes, electronic signatures are fully valid in Switzerland. ZertES governs recognition and technical standards. QES — when combined with a qualified timestamp — is legally equivalent to a handwritten signature. Mutual recognition of QES between Switzerland and the EU does not yet exist — negotiations were initiated in 2025.
Which signature do I need for an employment contract?
Employment contracts in Switzerland have no statutory form requirement (CO Art. 320) — they can even be concluded orally. An SES, AES, or QES can improve evidentiary standing but is not legally mandatory. Exceptions such as apprenticeship contracts (Art. 344a CO) do require written form.