The maximum claim is 45 pence per mile for genuine business use, but it surely isnt that easy?
Well, HMRC each year issues a data sheet of Advisory Fuel Rates, they are reviewed every three months and they take account of engine size, fuel type and current fuel prices.
Next, record every single mile that you do, the accuracy and detail of your records can be used as evidence in any argument with the HMRC. Now, assuming you stick to current AFR rates, tax and NIC are not applicable, so best to follow guidelines.
If your fuel is free, then you must discount your private mileage from your total use, then by applying the AFR you will have no free fuel tax to pay.
Suppose you use your own car and use it for work. Then the Authorised Mileage Allowance Payments (AMAPs) are used to calculate reimbursements. They are designed to cover the running costs including insurance, road tax and MOT . A little known additional claim is the 5 pence per mile that is available extra for any mileage with another member of staff.