If an electronic signature is challenged, four things matter: who signed, what they signed, when they signed, and whether they meant to sign. A good record answers each one with something other than your word.
In practice that means keeping the sealed PDF and its evidence certificate, not re-saving or printing the signed file, and storing copies somewhere safe. A screenshot of a signature, or a signature image pasted onto a page, answers none of the four. Courts weigh evidence, and no tool can promise how a judge will see a particular document.
The short answer
- Who: keep the signals that point to a person. The email address the signing link went to, the IP address, the device and the approximate location.
- What: keep the exact file, with a fingerprint (a hash) that shows it is that file and no other.
- When: keep a time that did not come from the person relying on it. A date typed on a page is only what somebody typed.
- Intent: keep a record that they agreed to sign, and what surrounded the signature: the invitation, the emails either side, and what happened next.
- Then store it. Keep the sealed PDF untouched, keep the certificate, and keep a second copy.
What gets questioned when a signature is disputed
Whether an electronic signature can count at all is rarely the question. For most documents the law answers it, and our guide to whether an electronic signature is legally binding in the UK covers it. The arguments are about facts. They come in four kinds.
- Who: “That was not me.” Somebody else had the inbox, the phone or the login. The useful evidence is the set of signals around the signing: the email address the link was sent to, the IP address, the device, the approximate location, and whether they fit how that person normally deals with you. No single signal proves who was holding the phone. Together they build a picture.
- What: “That is not what I signed.” A page was swapped or a figure changed, or the file in your folder is not the one that went out. The useful evidence is the exact file and its fingerprint. A different file gives a different fingerprint.
- When: “Not on that date.” The useful evidence is a time, and the question to ask is who supplied it. A time set by the person who benefits from it is weaker than a time set by somebody independent.
- Intent: “I never agreed to that.” The Law Commission’s 2019 statement of the law says an electronic signature is capable of executing a document where the person signing intends to authenticate it and any formalities are met. To decide whether a way of signing shows that intention, it says, the courts look objectively at all the surrounding circumstances. So the evidence is the circumstances: a record that the person agreed to sign electronically, the invitation they received, the emails before and after, and what both sides did next, such as paying a deposit.
The law does help on one point. Under section 7 of the Electronic Communications Act 2000, an electronic signature is admissible in evidence on questions of authenticity or integrity. Admissible means it can be put in front of the court. How much weight it carries is for the court. The Law Commission’s electronic execution of documents project page sets out the statement of the law in full.
Why a screenshot or a pasted signature is weak
A screenshot, or a signature image dropped onto a PDF, is a picture. It may still count as a signature. The trouble is how little it proves.
- It is not tied to the document. The same image can be moved to a different page or a different contract in a minute.
- It carries no record of who placed it, from what device, or from where.
- The time on it is whatever the file or the screen said, and either can be changed.
- Nothing shows whether the page around it was edited afterwards.
- If the other side says it is a forgery, you have little but your word to answer with.
What an audit trail adds
An audit trail is a log of what happened to a document: sent, opened, signed, sealed. Each entry has a time, and for a signer it can include the IP address, device and approximate location.
A plain log has a weakness. If it sits in one company’s database, somebody could change it, and you would have to trust that nobody did. Pixasign chains its events: every event carries the hash of the one before it, so changing an earlier entry would no longer match the entries after it. The final value of the chain is printed on the evidence certificate each party is sent. A later change to the record would not match their copy.
Before anyone signs in Pixasign, they agree to sign electronically, and the evidence certificate records that each signer “agreed to sign electronically”, with the time our server logged it. That is part of the evidence of intent. A trail still has limits. It records events. It cannot record what somebody had in mind.
What a sealed PDF adds
The audit trail says what happened. The sealed PDF is the document itself, with proof built into the file. When the last person signs, Pixasign seals the whole file with one timestamp from DigiCert, an independent timestamp authority. It is an RFC 3161 timestamp in the PAdES document timestamp format, and the validation data comes embedded in the PDF. Our guide to what PAdES is explains the format.
Change a byte the seal covers and it breaks; anything added later shows as a change at pixasign.co.uk/check.
The timestamp is applied once, at the end. The time of each earlier step is recorded by our server. Where each time comes from:
| Step | Where the time comes from |
|---|---|
| Document sent, link opened, each person agrees to sign and signs | Recorded by Pixasign’s server |
| Whole file sealed | DigiCert, independent of Pixasign |
The key that signs the timestamp belongs to DigiCert, not to us.
What Pixasign records, and what it does not
With the sealed PDF you get an evidence certificate. Both are sent to everyone who signed.
- Who signed, and the email address the signing link was sent to.
- When they opened it, when they agreed to sign electronically and when they signed, from what device, IP address and approximate location.
- A fingerprint of the document before and after sealing.
- The hash-chained events, with the final value printed on the certificate.
And what it does not do:
- It does not prove who the person is. Each signer is identified by the email address their link was sent to. If who holds that inbox is the question, add evidence from outside the tool.
- It does not prove authority. A sealed file does not show that the signer was allowed to sign for a company.
- It is not a qualified signature. Pixasign does not offer qualified electronic signatures. See simple, advanced and qualified signatures for what that means.
- It cannot witness a deed. Documents that need a witness are outside what Pixasign does. Formalities are a question for whoever drafts the document.
- It does not read minds. The record shows the signer agreed to sign electronically. Intent is still argued from all the circumstances, with the record as part of them.
Our security page describes how sealing and storage work, and the guide to electronic signatures for UK small businesses covers the law, the proof and the pricing together.
How to keep the evidence
Good evidence can be spoiled by how it is stored. Do this:
- Download the sealed PDF and the evidence certificate when the last person has signed. Keep them together.
- Do not edit, re-save or print the sealed PDF to a new PDF. A new PDF made that way is a different file. The seal belongs to the original.
- Do not rely on a printout. A printout or a scan is a picture of the document. Keep the digital file.
- Store two copies in two places, for example your own storage and a backup. Your own copy is the one you control.
- Keep the surrounding record. The email that sent the quote or contract, the replies, and anything that shows both sides acted on it.
- Check it once. Drop your downloaded copy into the checker so you know what a good answer looks like and that your stored copy still gives it.
If who signed matters a lot, add a step outside the tool, such as a call to a number you already hold for that person. Keep a note of when you did it.
How a counterparty can check it
A customer, an insurer or a solicitor can check a sealed file at pixasign.co.uk/check. It is free. There is no account, no sign-in and no card. They choose the PDF and get one of three answers:
- Sealed by Pixasign and unchanged.
- Sealed by Pixasign but changed since it was sealed.
- Not sealed by Pixasign. For a file with no Pixasign seal, that does not make it a forgery.
One thing to say plainly. The checker decides “sealed by Pixasign” from Pixasign’s own records. It is our check, not an outside one. The independent part is the DigiCert time inside the file. And a good answer is about the file. It does not prove who the signers are.
What it costs
The evidence certificate and the seal come with every plan. Pixasign is free for 1 user and 3 documents a month, with no card. Paid plans are one flat monthly price with unlimited users: £19 a month inc VAT for 50 documents, £59 inc VAT for 200 and £99 inc VAT for 500. Unlimited users means no charge per user: an account starts with room for 200 active people, and we raise that free on request. The people who sign never pay and never need an account.
See the record for yourself
Free for 3 documents a month, no card. Send one document for signature and read the evidence certificate that comes back.
Start free UK company. Documents stored in the EEA.Questions
- What is the best evidence of an electronic signature?
- No single item. A strong record answers four questions: who signed, what, when and with what intent. In practice that is the signing signals, the exact file and its fingerprint, a time from an independent source, a record that the signer agreed to sign electronically, and the emails and conduct around it. How a court weighs them is for the court.
- Is a screenshot of a signature enough?
- It may still count as a signature, but it proves little. It is not tied to the document, it does not record who made it, and the time on it can be changed. Keep the signed file and its record instead.