I have a client that owes roughly $45,000 from 2018. He got married in 2022. There are no dependents and are not concerned about the limitations of MFS. They are most concerned about the new wife protecting her 2022 refund from overpayment. 

Would it be best to file MFS or file 8379? Again, the primary concern is the refund for overpayment of 2022 taxes.