Interest accrues daily based on the remaining, unpaid principal balance. Each time a payment is made the funds are applied in the following order: 1) toward the accrued interest since the previous payment, and 2) remaining funds toward the unpaid principal balance and/or other fees as applicable.
If payments are not received by the scheduled due date, the final payment can differ from the scheduled payment amount that is listed on your loan contract. For example, if payments are made prior to the scheduled due date, less interest accrues and the principal balance will reduce at a faster rate. Conversely, if payments are paid after the scheduled due date, more interest accrues.