A co-signer is a person who agrees to be legally responsible for a loan along with the primary borrower — typically used when the primary borrower has thin credit or insufficient income to qualify alone. Co-signers are EQUALLY liable for the debt.
Co-signers commit their own credit profile + income to support a loan application that wouldn't qualify on the primary borrower's profile alone. If the primary borrower misses payments, the co-signer is legally on the hook for the entire balance. Common co-signer scenarios: - Parent co-signs a child's first auto loan or student loan to enable approval - Spouse with stronger credit co-signs a mortgage when the household income is split - Family member co-signs an apartment lease for someone with thin credit Risks for the co-signer: - Full legal liability for the debt if primary borrower defaults - The debt appears on the co-signer's credit report — affects their DTI when they apply for their own credit - Late payments by the primary borrower damage the co-signer's credit too - Removing yourself as co-signer typically requires the primary borrower to refinance the loan into their own name only (which requires their credit to have improved enough to qualify) Co-signing should be a deliberate, high-trust decision. Never co-sign for anyone you'd not personally lend the money to with no expectation of repayment. The CFPB's guide to co-signers (https://www.consumerfinance.gov/ask-cfpb/what-is-a-co-signer-en-1826/) explains co-signer rights and obligations under federal consumer credit law. The FTC's guide to credit rights (https://consumer.ftc.gov/credit-loans-debt) covers how co-signed debt affects credit reports under the Fair Credit Reporting Act.
Two ways. (1) The new account adds a hard inquiry to your report (5-10 point dip, recovers in 12 months). (2) The new debt counts toward your debt-to-income ratio for any future credit application you make. If the primary borrower makes on-time payments, the co-signing experience is neutral-to-positive. If they miss payments, your credit takes the hit too.
Typically requires the primary borrower to refinance the loan into their own name only — which requires their credit + income to qualify on their own. Some loans have explicit 'co-signer release' provisions after a defined number of on-time payments (typical for student loans). Most other loans require full refinance.