Check with your accountatnt,but if you put that vehicle into service,meaning ready to haul your first load,before Dec.31st,you could write that truck off for the entire year,meaning depreciation and interest,of course you want have paid any interest yet,but you can do the depreciation thing.If you lease the truck,you can only write off the lease payment for that month,also,if your on a lease purchase,then the write off is as if it were a buy,and that is only depreciation and interest,not the lease payment.