SES, AES and QES: Understanding Electronic Signature Levels

Three levels of electronic signatures under eIDAS

The EU's eIDAS Regulation defines three levels of electronic signatures: Simple Electronic Signature (SES), Advanced Electronic Signature (AES), and Qualified Electronic Signature (QES). Each level adds requirements that increase the signature's reliability and legal weight. Many non-EU jurisdictions use a similar three-tier framework.

SES vs AES vs QES

	Legal weight	Key requirements
SES	Valid but lowest evidence weight	Any electronic method expressing intent
AES	Stronger — linked to signer, tamper-detectable	Uniquely linked, under sole control, identifiable
QES	Equivalent to handwritten signature	AES requirements + qualified certificate from accredited CA

Simple Electronic Signature (SES)

The most basic form of electronic signature. No specific technology or identity verification is required.

Any data in electronic form attached to or logically associated with other data, used by the signatory to sign. This covers typed names, clicked checkboxes, email confirmations, and scanned signature images.

SES is valid for most transactions under eIDAS Article 25(1). However, it does not carry any special legal presumption. Its evidentiary weight in court depends on the surrounding circumstances: was the signer's email verified? Was an audit trail maintained?

Internal approvals, NDAs, policy acknowledgements, low-value transactions, consumer click-to-accept. Anywhere the risk of repudiation is low and the cost of stronger signatures is not justified.

SES does not prove signer identity (anyone with email access could sign), does not detect document tampering, and is easily repudiated in court. Not suitable for high-value contracts, regulated filings, or documents likely to be disputed.

Advanced and Qualified signatures

AES and QES add specific technical and procedural requirements that make signatures more reliable and harder to challenge.

AES — Advanced Electronic Signature

AES must be: (1) uniquely linked to the signatory, (2) capable of identifying the signatory, (3) created using electronic signature creation data under the signatory's sole control, and (4) linked to the document so that any subsequent change is detectable. AES typically uses PKI-based digital signatures but does not require a qualified certificate.

QES — Qualified Electronic Signature

QES meets all AES requirements plus: it is created by a qualified electronic signature creation device (QSCD) and based on a qualified certificate issued by an accredited Trust Service Provider (QTSP). Under eIDAS Article 25(2), QES has the same legal effect as a handwritten signature.

When QES is legally required

Some EU member state laws require QES for specific document types: certain employment contracts, consumer credit agreements, land transfers, and documents requiring notarisation. Outside the EU, similar requirements exist: China's reliable e-signature, Singapore's QES for certain filings, Malaysia's DSA digital signature.

The cost-benefit tradeoff

SES is nearly free. AES adds modest cost (PKI infrastructure, identity verification). QES is the most expensive (qualified certificate, QSCD, QTSP fees). Match the tier to transaction risk: SES for low-risk, AES for standard commercial, QES for high-value or regulated.

Signature tier data: identity proofing cost and time by level

Concrete identity proofing requirements and costs for each tier.

Identity proofing time by tier

SES: 0 seconds (no identity proofing required). AES: 30-60 seconds via eKYC (document photo + selfie). AES via national eID: 5-15 seconds (Singpass, iAM Smart). QES: 2-10 minutes first-time (one-time registration with QTSP), then <5 seconds for subsequent signatures. For high-volume operations (100+ signatures/day per signer), QES one-time registration amortises to near-zero per-transaction cost.

Regulatory mapping by document type

EU: consumer credit agreements require QES (Consumer Credit Directive). Employment contracts: AES sufficient in most EU countries. Real estate: QES required in Germany, Spain, Italy; AES accepted in France, Netherlands. APAC: Singapore MAS-regulated products require QES for account opening. Hong Kong: AES for most commercial; QES not available locally (no QTSP). China: CA-backed reliable signature for government filings.

Common questions

Simple Electronic Signature. It is the most basic e-signature level under eIDAS — any electronic method of expressing intent to sign, with no specific technical requirements.

How eSign.AI applies this in practice

eSign.AI supports all three tiers with per-workflow configuration: SES for low-risk documents, AES with eKYC for standard contracts, and QES via accredited QTSPs for high-value and regulated transactions.

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