SQL Server Service Account login or password is not valid error I am trying to install SQL Server 2012 Express on a Windows 2012 Server for test purposes. This machine is part of our company domain. 

During installation I am trying to use one of domain account for SQL Server Database Engine service but it is failing with following error, 


  "The SQL Server service account login or password is not valid. User
  SQL Server Configuration Manager to update the service account."


I have verified both domain user and password. And this account has "Log on as a Service" permission enabled. I have also added this user into local admin group but still no go.

Any suggestion is appreciated.
The issue isn't with the account you are attempting to use, but your account. If you look in the setup log file, which is created during the installation of the SQL Server application, you will see the details of the issue, with technical jargon that will indicate the issue is probably a permission issue with your account having permission to perform a check on the service account credentials:

Slp: Sco: Attempting to check if container ‘WinNT://DOMAIN’ of user account exists
Slp: UserSecurity.ValidateCredentials — Exception caught and ignored, exception is Access is denied.
Slp: UserSecurity.ValidateCredentials — user validation failed


Rebooting usually fixes this issue, as does changing the service account value after installation is complete. A minor issue that sometimes appears.