Ideally, you want your extra payments to go towards the principal amount. However, many lenders will apply the extra payments to any interest accrued since your last payment and then apply anything left over to the principal amount. Other times, lenders may apply extra funds to next month's payment.
First, you'll need to contact your lender and let them know you want the information. Depending on your lender, you may have to sign in to an online account, call a helpline, or send a formal letter to start the request process.
Under federal law, the servicer must generally send you a payoff statement within seven business days of your request, subject to a few exceptions. (12 C.F.R. § 1026.36.)