# AA24 signature error

`AA24 signature error` is an ERC-4337 EntryPoint error that means the smart account's `validateUserOp` function rejected the user operation's signature.

The `validateUserOp` function of the smart account rejected the signature of the user operation.

## Possible solutions

* Verify that the user operation was correctly signed, and that the signature was correctly encoded in the `signature` field of the user operation.
  * Most smart account implementations sign over the `userOpHash`. Make sure that the `userOpHash` is correctly computed. Consider leveraging functions like `getUserOperationHash` from `viem/account-abstraction`.
  * Make sure you have selected the correct `chainId` and `entryPointAddress` when computing the `userOpHash`.
  * Make sure the smart account signature verification function is correctly implemented.
* If all else fails, investigate why the `validateUserOp` function rejected the user operation signature using tools like [Tenderly](https://tenderly.co/).