You can pay in the lump sum or the payments can be spread over the remaining monthly payments. Please note, these miles are not refundable if you do not drive the additional miles that are purchased. Mileage must be purchased at least ONE business day prior to the maturity date or vehicle return date (whichever comes first). You can purchase miles on the website up to 120 days prior to maturity. Inside of 120 days to maturity, you must call Lease End directly to purchase.