Comparing the Three eIDAS Signature Tiers
Quick Answer / Definition
Under UK eIDAS, Simple Electronic Signatures (SES) cover everyday contracts, Advanced Electronic Signatures (AES) add unique cryptographic keys, and Qualified Electronic Signatures (QES) require identity verification by a regulated trust authority.
Many businesses mistakenly assume that only expensive Qualified Electronic Signatures (QES) are legally binding. In reality, Article 25(1) of UK eIDAS states that no signature can be denied legal effect simply because it is an SES.
Over 95% of business-to-business and business-to-consumer contracts in the UK—from quotes and variations to NDAs and consultancy retainers—are executed quickly and legally with SES.
| Signature Tier | Legal Definition | Typical Use Case | Signer Friction |
|---|---|---|---|
| Simple (SES) | Electronic mark logically associated with data (ECA 2000 s.7) | Quotes, trade contracts, NDAs, invoices, HR policies | Low (Under 30s) |
| Advanced (AES) | Uniquely linked to signatory with tamper detection | High-value cross-border banking, intellectual property assignments | Medium (2–5 mins) |
| Qualified (QES) | Created by qualified signature device with trust certificate | Statutory cross-border court filings, regulated deeds | High (Requires ID check) |