Hi.Assuming you use your own car, you can claim tax relief on 45p for the first 10,000 business miles and on 25p per business mile less the amount paid to you by your employer. Take a look here for more information. HMRC give you tax relief on those figures. They don't pay you those figures.Complete and submit an online P87 to HMRC for each tax year back you want to make a claim for. There is a paper version here. You can only go back to 2010/11 as you will see here.I hope this helps but let me know if you have any further questions.