What factor primarily influences a borrower's credit score?

Payment history is the most significant factor influencing a borrower's credit score. This component accounts for about 35% of a FICO credit score, which is the most commonly used scoring model. A strong payment history indicates to lenders that a borrower is responsible and dependable in meeting their financial obligations. Timely payments on loans and credit cards help to improve the score, while late payments, defaults, and bankruptcies can severely damage it.

Other factors, such as the length of employment, type of mortgage applied for, and loan-to-value ratio, play roles in the overall lending decision but do not have as direct an impact on a credit score as payment history does. Length of employment may suggest job stability but does not reflect financial behavior. The type of mortgage and loan-to-value ratio are more relevant to the mortgage application process itself rather than directly affecting the borrower's creditworthiness as measured by the credit score.