Unless I'm the one who initiated the transaction (like making an online payment through an insurance company's customer portal. for example), I get instantly suspicious of anyone asking me for my bank account information. If you were making electronic payments to the original loan holder from a bank account, and that original loan holder sold your account to a new institution, then I have to think that the new institution would already have all of your account details, payment history, bank account info, payment methods, etc. If they didn't have your bank account information, why would they be asking about for it, unless you were setting up an online payment account? They don't need that information; all they should care about is that you're making timely payments on your loan. I'm not an expert on financing and I've never financed one through a dealership, but why would the holder of a loan want to know what your bank account number was?