Signed by both parties — what it really means
Two signatures on one document, or two matching copies each signed once? Whether a contract needs both signatures at all? Here's what the phrase means in practice, what changes when you sign by PDF, and how to make sure you end up holding a complete, matching copy.
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Is your copy complete?
- Every party named in the signature blocks has signed, and nobody signed in someone else's block.
- Anyone signing for a company shows their name and title, so it's clear they signed on its behalf.
- Each signature is dated, and any handwritten changes are initialled by both sides.
- All pages and attachments are present, and the text matches the version everyone agreed.
- Every party has received the final version — not just the person who signed last.
Updated 27 October 2026 · Written by Joe Farwick, who runs this site
What the phrase means
A contract is "signed by both parties" when each party that the contract names as bound by it has signed the same agreed text. With three or more parties the wording becomes "signed by all parties", and the idea is the same: nobody named in a signature block is missing.
"Duly signed" adds that the signatures were made properly — by the right person, in the right capacity and in the required form. Duly means "in a due manner", so a contract duly signed by both parties is one where, for example, the company's side was signed by someone authorised to sign for it, not by whoever happened to be at the desk.
Two ways to get there
One document, signed in turn. Party A signs the PDF and sends it to Party B, who countersigns the same file and sends the finished version back. Everyone ends up with a single document carrying both signatures. This is the simplest route and the one most people picture.
Counterparts. Each party signs its own identical copy, or just the signature page, and the copies are exchanged. Together they form one agreement. It's useful when people sign at the same time in different places, and many professionally drafted contracts contain a clause allowing it. The counterparts guide on this site covers how to do it cleanly.
Does a contract need both signatures to be valid?
Not always. A contract generally comes from agreement — an offer that is accepted, with something of value exchanged — and the signature is evidence of that agreement rather than the agreement itself. Informal deals without any signature can be binding.
Where the law demands a signed writing, it often only demands the signature of the party it's enforced against. The US Uniform Commercial Code's rule for sales of goods of $500 or more, for example, requires a writing "signed by the party against whom enforcement is sought". So a contract signed by one side may still bind that side.
The contract's own words can change this. Many say they become effective only when signed by both parties, or that the offer lapses unless countersigned by a date. Then a missing signature matters a great deal. If the stakes are high and one signature is missing, get legal advice rather than assuming either way.
Who keeps the original?
On paper, parties often sign two originals ("in duplicate") so each keeps one with ink signatures. With PDFs the question mostly disappears: each party keeps an identical copy of the fully signed file, and those copies are as good as each other.
What matters is that the copies really are identical. Save the executed PDF exactly as it was sent round — don't re-export, compress or annotate your record copy — and store it with the emails that delivered it. If the other side signed with a certificate-based digital signature, keep their file untouched so the signature still validates.
Open the contract the other party signed, place your countersignature and the date in your own block, and download the fully executed copy for every party.
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Two-signature questions
Is a contract valid if only one party signed it?+
It can be, depending on the law and the wording. A signature is evidence of agreement, and some rules only need the signature of the party being held to the deal. If the contract says it's effective only once both parties sign, it isn't complete until then.
Is it fine if one of us signs on paper and the other signs the PDF?+
For most everyday contracts, yes — one side can sign by hand and scan the page while the other signs the PDF. Agree it in advance, and check nothing in the contract or the law requires a particular form.
Do both signatures need the same date?+
No. Each person dates their own signature, so the dates often differ by days. An effective-date clause, if there is one, says when the contract starts; if there isn't, agree the start date in writing rather than guessing.
Who should send the fully signed copy?+
Usually whoever signs last, because they're the one holding the complete document. If you countersign, send it straight to everyone.
What does it cost to add the second signature here?+
Adding your signature to the PDF they already signed is free to try. To download the fully signed copy you subscribe for €2.99 a month or €24.99 a year and can cancel whenever you like — the plan runs to the end of the period you've paid for.
Add the second signature
Open the PDF they signed above — their signature stays in place.
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