There are lots of ways, the one that has worked well for me is: I'm a sales rep & take a vehicle allowance instead of a company vehicle. I did a log book for 6 months that gave me a 97% business use figure but I only claim 95%. (just to be safe) I use a chattle mortgage so I claim the total interest paid per tax year. Then, I claim 95% of every other item for the car. Everything! even 95% of licence fees etc etc. Then, you also claim the depreciation which I understand is a fixed componant that your accountant will know. Seems to help get me a healthy refund every year. And mate, just make sure you have reciepts for anything claimed.