by King_Maker on Thu Dec 29, 2005 12:52 pm
As your employer does not pay the maximum Approved Mileage Rates (40p per mile for the first 10,000 miles, 25p per mile thereafter), you can claim any difference on form P87 or your Self Assessment Return.
HMRC's booklet 480 "Expenses & Benefits" has more detail and is downloadable from their website.
http://www.hmrc.gov.uk/leaflets/menu.htm
This assumes that your Car Allowance has been subject to PAYE.