Appellate Practice Attorney serving New York, NY
Yes. You don't say why the co-signer wants to sue the primary signer, or what they both signed, but I will assume that they signed some form of promissory note, and the co-signer has paid on it while the primary signer has not. The cosigner can sue the primary signer for the amount the co-signer has paid the creditor above what he was supposed to. Thus, if the co-signer was supposed to have paid half the debt and had to pay all of it, he can sue the primary signer for the extra half; if the primary signer was supposed to be primarily responsible, and the cosigner was just a guarantor, he can sue the primary signer for any amount of the debt he, the cosigner, has paid.
Answered on Aug 28th, 2013 at 12:30 PM