International Standard Recording Codes
The US ISRC agency has begun charging a one-time fee of $80 for the allocation of a Registrant Code. It is not required that your master include codes. Please review the section on the website below regarding ISRCs. If you have previously acquired an ISRC registrant code, you can probably use the same one assuming the recording owner is the same. Again, please review the ISRC section on the website below for more details.
To obtain an ISRC registrant code in the US go to: http://www.usisrc.org/