Another person or individual other than the borrower who signs for a loan or promissory note and assumes equal liability for it. This is also referred to as a co maker. In many cases, the cosigner signs for a borrower who does not have collateral or good credit history. The cosigner guarantees that the loan will be repaid if the borrower fails to make payments. Normally, the cosigner is required to go through the same application and approval process as the original signer of the loan. A cosigner can’t improve your credit report but can improve your chances of getting a mortgage.