There is a code to report as "relationship with account terminate" and it would be the ECOA code of 'T' Terminate.  You can get there using Tool #51 Miscellaneous Loan Maintenance, selecting Additional Signers, selecting your signer, and selecting an ECOA code of 'T'. 

We would recommend changing the code prior to month end, then removing the additional signer after the 1st of the following month.