QES capabilities and limitations

Signature Requests with QES level have intrinsic security and compliance constraints. They must hence follow these rules:

Rules

• Signers must be sequential: only one Signer can act at a time. When using standard ordering (custom_recipient_order = false), set ordered_signers: true on Initiate Signature Request. When using custom ordering (custom_recipient_order = true), ensure no two Signers share the same step (via group_with_id).
• Authentication is not managed by OTP.
• There is an identity document and a video authentication.
• All Signers must use the same signature level qualified_electronic_signature(you can omit the field signature_authentication_mode or set it as null). Refer to Set the signature level for an API call example.
• Available in Sandbox once activated by our support. Consult our Qualified eSignature guide for more info.
• A Signer has 30 minutes to sign the Signature Request after a successful identification, to preserve signature integrity.

Allowed authentication modes

• null

Allowed types of signature interface

• ✅ Signature link delivered via email by Yousign

• ✅ Signature link delivered by you

• ❌ Signature interface embedded in iFrame

  • The signing flow cannot be iFramed. This limitation is linked to security constraints around identity verification. You should instead use redirect URLs to set up your signature user journey. Learn more about redirecting signers.

• ❌ Custom-made signature interface

Download the Verified Identity Proof for a succeeded identification

You can download a Verified Identity Proof in PDF format for a signer identified as part of a Qualified Electronic Signature (QES) flow. The PDF contains the identity verification report and supporting identity documents collected during the Video Verification session. If the User has used the Saved Identity to perform the QES, the Verified Identity Proof won’t be available.

To use it, listen to the signer.identification_succeeded webhook (see reference). Once received, you can call the endpoint to download the PDF (see reference). In most cases the proof is generated within a few seconds; if it’s not available immediately, retry after a short delay.

The Verified Identity Proof is available only if:

• Have at least the API PRO plan;
• The Signer’s identification succeeded;
• The Signature level is QES;
• The identification method used by the User is Video Verification (not a Saved Identity);
• The identification data has not been anonymized (availability is limited to the provider retention window, currently up to ~3 months);
• The related Signature Request has not been permanently deleted.

🚨 This PDF contains highly personal data. Download it only when necessary and store it securely if you need to keep it beyond the provider’s retention window.

How the Signature works with multiple fields

With QES, a single cryptographic Signature is issued for the entire Document, regardless of how many Signature Fields it contains. All signature images visible on the Document are covered by that single technical Signature.

This differs from Simple Electronic Signature (SES) and Advanced Electronic Signature (AES), where each Signature image is linked to its own technical Signature directly. The legal requirement is identical: one technical Signature is sufficient for a valid Electronic Signature.

When a QES Signature Request contains multiple Signature Fields, the same Signature image is applied to every Field as a stamp.

Signature panel behavior

When a QES Document contains multiple Signature Fields, clicking on a Signature image in an external PDF reader will not open the Signature verification panel. This is because the Fields are converted strictly into images, and the document is signed as a whole just once, without any direct link to the fields. It has no impact on the legal value, it’s only a technical choice from us: the Signature remains valid and the Signature panel can be opened manually.

Locked PDF documents

Some PDF documents are locked according to the PDF specification (for example, a document already signed by a third-party tool). For QES Signature Requests, locked PDFs only support one Signature Field.

If you attempt to add more than one Signature Field or a stamp to a locked PDF, the API returns the following error:

"This PDF document does not support multiple signature fields. Only one signature field is allowed."

This constraint applies only to QES.
SES and AES Signature Requests support multiple Signature Fields on locked PDFs.