To sign a 2-of-3 Bitcoin multisig transaction, you start with one unsigned transaction, then collect valid signatures from any two of the three authorized keys. Once the second signature is attached, the transaction can be broadcast to the Bitcoin network.
What 2-of-3 multisig actually means
A simple way to picture it: three keys exist, but only two are needed to open the box. Bitcoin multisig works in that same spirit. Control is shared, so one person cannot move the funds alone.
That does not mean there are three copies of the same wallet floating around. The coins are locked by a spending rule. That rule says two valid signatures out of three possible signers must approve the transaction before the network will accept it.
Small difference. Big consequence.
The signing flow from start to finish
People often treat signing as one click at the end. With multisig, the signing step is only part of the job. The real process begins earlier, when someone creates the transaction that everyone else will review.
- Create the unsigned transaction. One participant, or a wallet that supports multisig, prepares the payment by setting the destination address, the amount to send, and the mining fee.
- Review the full transaction details. Each signer should inspect the recipient address, the amount, the change output, and the fee. If any of those details are wrong, a valid signature would still be approving the wrong transfer.
- Add the first signature. One key holder signs with their own key, often through a hardware wallet or multisig-capable software wallet. The transaction is still incomplete at this point.
- Pass the same transaction to a second signer. The second key holder reviews it again and adds another valid signature.
- Check whether the threshold is met. Once two signatures are attached, the transaction satisfies the 2-of-3 requirement.
- Broadcast the finished transaction. Whoever has the fully signed version can send it to the Bitcoin network. That person does not have to be one of the signers.
The order of the two signers usually does not matter. Independent review does.
What you are approving when you sign
A multisig signature is not a generic vote. It is tied to a specific transaction. Change the details, and the previous signature usually stops being useful for that altered version.
- The inputs: which unspent outputs are being spent.
- The outputs: where the bitcoin is going, including any change output.
- The fee: how much value is left for miners.
- The script conditions: the funds were locked with a rule that requires two signatures out of three.
This is why “I already saw it earlier” is not enough. A signer should verify the exact version in front of them, not rely on memory or chat messages about what the transaction was supposed to do.
Why a signed multisig transaction may still fail
Most multisig trouble comes from mismatch, not mystery. Someone signs one version, someone else checks another, or the file being broadcast is only partially signed. From the outside, all of those can look like the same problem.
| Issue | Likely cause | What to check |
|---|---|---|
| Cannot broadcast | Only one valid signature is attached | Confirm that two authorized signers have signed the same transaction |
| Signature seems ignored | The transaction was edited after an earlier review | Make sure all signers used the same current version |
| An unfamiliar address appears | It may be the change output | Separate the recipient output from the return output before signing |
| One wallet will not read the file | Import and export formats may differ | Test compatibility before moving real funds |
| Broadcast still fails after two reviews | The version being sent may not be the fully signed one | Check that the file or transaction text includes both signatures |
There is a practical lesson here: “reviewed by two people” is not the same thing as “signed twice on the same transaction.” Multisig cares about the second one.
FAQ
Do all three people need to be online at the same time?
No. A 2-of-3 Bitcoin multisig transaction can be signed in sequence. As long as the same unsigned transaction reaches two authorized signers, they can approve it at different times.
What should one signer check before adding a signature?
The key items are the destination address, the amount, the change output, and the fee. A signer should verify those details directly in the wallet or device interface rather than trusting a message from another participant.
Why can’t the transaction be sent after one person signs it?
Because the spending rule has not been satisfied yet. One signature only creates a partially signed transaction, and Bitcoin still requires the second valid signature before the funds can move.
Can I broadcast first and collect the second signature later?
No. The network expects the transaction to meet its spending conditions before broadcast. For a 2-of-3 setup, that means the second signature must already be part of the final transaction.
Can the two signers use different devices?
Yes, and that is common. The only catch is coordination: both devices or wallets must be working with the same multisig setup and the same transaction version.
Safer habits before you move serious funds
Clear roles help more than people expect. Decide who builds the transaction, who performs the second review, who stores the partially signed file, and who sends the final version. Confusion in those handoffs causes plenty of avoidable mistakes.
For a first live run, use a tiny amount and walk through the full cycle: create, export, sign once, sign again, verify completion, then broadcast. That rehearsal shows each participant exactly where their responsibility begins and ends.