£300 a month is pretty cheapskate. I guess the company car choice is Hyundai i10, Kia Picanto, used Ford Fiesta, Dacia Sandero to match that level of funding? I get £750 a month and that with business mileage pays about half the total running costs of a £25k Hyundai Santa Fe with no service costs (prepaid) Depreciation is your biggest cost and if you're going to be doing a lot of business miles that will hurt the value of your car. i suppose if you were going to buy one then whatever you get from the company is a bonus but it is still a bit mean. Very nice car btw, says you're earning a good packet, know a bit about cars and can afford a top quality one. That may or may not be the impression you want to make away from the office.

By my calculations (happy to be corrected if wrong):

Car allowance only just puts OP into 40% bracket (by about £150) and NI of 2% would be payable on the allowance.

So worth approx £231.50 pm take home.

You need to compare this to the tax you would pay on a company car and see if the difference finances the car you want. Bear in mind business mileage would be paid at probably 45ppm on your private car and about 15ppm on a company car. Factor in maintenance, insurance. depreciation etc if going private.

Tax on a petrol 335 would be fairly meaty but as discussed above I doubt that's what's on offer if the CA is £300pm

>>The car/car allowance plus your salary puts you into the 40% tax bracket, so your car >>allowance of £300 per month

I think not

40% rate is payable after taxable income is around £40K.....The annual Personal Allowance + Pension contributions mean you typically have to earn at least £50K+ to pay 40%