Even with a perfect repayment history, your score is highly sensitive to your daily financial behavior. Common reasons for a sudden drop include:
High Credit Utilization: You used more than 30% of your total available credit card limit. Lenders view this as being reliant on credit.
New Hard Inquiries: You recently applied for a new loan, credit card, or pay-later service. Every new formal application temporarily docks your score.
Closing an Old Account: Shutting down your oldest credit card reduces your "average age of credit," which negatively impacts your score.
Co-signing a Loan: If you are a guarantor for someone else's loan and they defaulted, your score will drop too.