by mullet on Sun Jan 29, 2012 9:41 pm
You firstly need to check your contract or terms/conditions of your employment to see whether you are entitled to claim reimbursement from your employer. If travelling is an inherent part of your job, then it is surprising (but not unheard of) for you to be able to claim nothing. That is the best option for you - for instance if you travel 15,000 allowable business miles in a year then you receive 10,000 @ 45p = £4,500 plus 5,000 @ 25p = £1,250 = total £5,750 received and such amount would not be subject to tax or NICs.
If you receive nothing from your employer, then you get tax relief on £5,750 at your highest rate of tax. So perhaps £5,750 @ 20% = £1,150 in your pocket. But the fuel alone would have cost you 15,000 x 15p per mile = £2,250.
The same principle broadly applies to mobile phone call costs. If your employer reimburses nothing, then you get tax relief on the relevant amount - you do NOT claim "reimbursement" from HMRC.
You claim on form P87, use this URL. http://www.hmrc.gov.uk/forms/p87.pdf
But if your expenses exceed £2,500 you will have to complete self assessment returns.