Mixed files merge strangers' debts onto your report if 7 of 9 SSN digits match

Credit bureaus use probabilistic matching algorithms that consider a 7-out-of-9 digit SSN overlap a "complete match," causing two different people's credit files to merge into one. Fathers and sons with the same name, people with common Hispanic surnames, or anyone who shares a former address with a stranger can wake up to collections, late payments, and accounts they have never seen. Fixing a mixed file requires disputing each incorrect tradeline individually across all three bureaus, a process that can take months while the victim is denied mortgages or charged predatory interest rates. The problem persists because the bureaus prioritize ingesting billions of data points quickly over investing in deterministic identity resolution, and because FCRA lawsuits over mixed files are settled quietly without forcing systemic changes to the matching logic.