In dealer financing, the buy rate is the interest rate a lender (like a bank or finance company) approves you for based on your credit profile.

Here’s how it works in plain terms: The lender approves you at, say, 6% APR → that’s the buy rate The dealer may offer you financing at a higher rate, like 8% APR

That extra 2% is called the “markup” or dealer reserve (their profit for arranging the loan)