# AA25 invalid account nonce

`AA25 invalid account nonce` is an ERC-4337 EntryPoint error that means the user operation's `nonce` is not a valid next nonce for the smart account.

The `nonce` of the user operation is invalid.

## Possible solutions

* Verify that you are using the correct `nonce` for the user operation. The `nonce` should be the current nonce of the smart account for the selected `key`. Consider leveraging functions like [`getAccountNonce`](/references/permissionless/reference/public-actions/getAccountNonce).
  * Make sure that you are not reusing a nonce that has already been used.
  * Make sure that you are not using a nonce that is too far in the future (more than 10 higher than the current nonce).
* Verify that the nonce is formatted correctly.
* Use custom nonce `key` to send parallel transactions. See [How to Send Multiple Transactions](/references/permissionless/how-to/parallel-transactions##sending-multiple-transactions-in-parallel).

:::info
Instead of sequential nonce the EntryPoint implements a nonce mechanism that uses a single `uint256` nonce value in the user operation, but treats it as two values:

* 192-bit `key`
* 64-bit `sequence`

For each `key` the `sequence` is validated and incremented sequentially and monotonically by the EntryPoint for each user operation, however a new `key` can be introduced with an arbitrary value at any point.
:::