Claimed for the last 6 years.
1. It has to be duty mileage - not sports, medical or training.
2. You need to be a Top Rate Tax Payer.
3. You can include it as part of your tax return.
4. If not, the form is a P87 - available from the HMRC web site, complete with the guidance.
5. You may be requested to provide details of each and every journey you use your own car (date, travel to/from, reason, mileage, reimbursement received through JPA).
Hope this helps!