If you are aware that you have the incorrect Auth Codes, you will have to contact your registrar and request a new code. You can find how to do this here: How do I transfer an existing domain to MyHost?
Auth Codes for some Top Level Domains expire, .nz for example, so if your Auth Code is more than 30 days old then you will need a new one before any transfer can take place. Only one code is valid at a time.
