What a certificate of completion proves — and what it does not

The document you hand to a court, a bank or an auditor, and the one question to ask of it before you rely on it.

A certificate of completion is the summary page attached to a finished agreement: who signed, when, from where, how they were identified, and a hash of the finished document. It is the artefact people actually produce when a document is questioned.

What should be on it

• Every participant, their role, and whether they were required to act
• Each one's outcome and its timestamp — signed, approved, declined, skipped
• The assurance level applied to each, and whether it was met
• The document, by name and content hash
• The routing that was in force, including any condition that skipped somebody
• A completion hash, and a statement of what that hash covers

The claim worth checking

Most certificates carry a line like "recompute this hash to confirm nothing has been altered." That sentence is only true for the facts the hash actually covers.

It is very easy for these to drift apart. Somebody adds a field to the certificate — a reviewer's required flag, say — and does not add it to the hashed record. Nothing fails. No test complains. The certificate now makes a claim outside its own seal, and the sentence under it is wrong. Anyone editing that field would be editing a document that still verifies.

So the question to ask is narrow and specific: is every claim on this certificate covered by the seal, and how do you know?

The good answer names a mechanism. One definition of the seal, called by the thing that seals, with a test that edits each fact in turn and asks verification whether it noticed — so a fact added and left out fails immediately rather than in a dispute.

Seals that grow

There is a second problem with sealing, and it has a bad failure mode. If the definition of what a seal covers changes — usually because it grew to cover more — then certificates issued under the old definition no longer match the new one.

Telling somebody their certificate was altered when in fact the seal merely grew is a false accusation about a genuine document. A system that takes this seriously keeps every historical definition, recognises which one a certificate was sealed under, and says so, rather than either waving it through as current or declaring it tampered with.

What a certificate does not prove

It does not prove the signer had authority to bind their organisation. It does not prove they read the document. It does not, by itself, establish legal validity — that depends on jurisdiction, document type and how the transaction was carried out.

What it does is make the facts checkable. That is a smaller claim than "legally binding", and a far more useful one, because it is true.

Last reviewed 2026-09-18. Pactlyra produces a detailed evidence record for every completed document. Electronic signature validity depends on your jurisdiction, the document type, and how the transaction is carried out; nothing here is legal advice.