ERR_ACCOUNT_LOCKED on Xero: Account locked. Root cause: The accounting period or account has been locked for period close, year-end processing, or audit purposes. Locked accounts and periods prevent any further transactions from being posted to maintain the integrity of financial statements that have already been reviewed or published. Step 1: Check lock status. Verify account is locked Step 2: Unlock account. Remove lock if authorized Step 3: Wait for unlock. If locked by system Step 4: Contact admin. Request unlock if needed