Advanced Electronic Signature

An AES sits one rung below qualified. It has to be linked to the signer, capable of identifying them, made using something under their sole control, and connected to the document so any later change is detectable. Those requirements are spelled out in Article 26 of eIDAS. The key difference from a QES is that an AES does not demand the certified hardware and formal identity vetting, so it is easier to use while still offering strong assurance.

Varies by region. Like QES, this is an EU and UK tier that the US does not formally define. The requirements are identical in wording under EU eIDAS and UK eIDAS, since the UK inherited the text; the practical divergence is about cross-border recognition rather than the definition itself.