Should I tell the dealer I'm paying cash?

Many buyers prefer to settle the out-the-door price first and then say how they will pay, so the price discussion stays separate from financing. Some advertised discounts depend on financing with the dealer's lender, so ask whether the price changes based on payment method. There is nothing wrong with being upfront; just make sure the final number is the same either way and get it in writing. Large cash payments may require identity paperwork under federal reporting rules.