How to verify a signature: a practical guide

Start with the right comparison

A signature is only “right” or “wrong” compared with something. The best comparison is a set of genuine signatures by the same person. These are called reference signatures.

A single specimen card is a weak basis. People sign differently on a form, a phone screen and a cheque. Several references, made in similar settings, show how that person really signs.

The signature you are checking is the questioned signature. Keep it and the references side by side, at a similar size.

What to look at by eye

Work from the overall picture down to the detail. Look at each of these in the questioned signature and in every reference:

• Overall shape: the outline, the size and the angle of the whole signature.
• Proportions: how tall the capitals are next to the small letters, and how wide each part is.
• Letter shapes: how each letter is formed, including the ones people simplify.
• Stroke flow: where the pen joins letters, where it lifts, and the order the strokes seem to follow.
• Line quality: a practised signature is smooth and confident. Shaky, slow or patched lines stand out.
• Starts and ends: a fluent stroke often starts and finishes with a taper. A blunt start can mean a careful, slow copy.

Where the image allows it, pen pressure and pace can help too. Thicker, darker lines usually mean more pressure. A phone photo or a scan often hides both.

Expect natural variation

Nobody signs exactly the same way twice. Genuine signatures vary a little in size, slant and spacing. Your references show how much this person usually varies.

That cuts both ways. A signature far outside that range needs a closer look. So does one that matches a reference almost perfectly. A near-exact match can be a photocopy, a scan or a tracing of that reference.

Warning signs of a forgery

• Slow, even strokes with little variation in width, which can point to tracing.
• Hesitation marks, pen lifts in odd places or retouched lines.
• A signature that overlays one of the references almost exactly.
• On a digital document, a box or background around the signature that differs from the page, which can mean a pasted image.
• Letter forms or proportions that the person never uses in any reference.

One warning sign is not proof. Treat it as a reason to look again, gather more references or escalate. Our guide to detecting forged signatures covers each kind in more depth.

Record what you decided, and why

A tick on a form tells an auditor very little. Write down which references you used, what you looked at and why you reached your decision.

If you work to a policy, say which one. The same record helps the next person who looks at a disputed signature.

When to escalate

Pass a signature on when:

• it matters in a legal dispute, or someone may challenge the decision;
• the paper, ink or pen pressure is in question, which needs the original document and a forensic document examiner;
• you have no genuine references, or too few to judge the person’s usual variation;
• you are unsure. Unclear cases are the ones a second person should see.

Checking signatures at volume

Checking by eye works for a handful of signatures a week. At volume, reviewers tire and results drift. Software can do the first pass the same way every time and send the unclear ones to a person.

Unforged Nib compares each signature with the person’s own references and returns one of six verdicts, with reasons. FAILED always goes to a person. It is never an automatic rejection. See how it compares with checking by eye.