Many thanks for your reply.
Fully understand re: the inability to claim mileage allowance/ fuel costs with respect to my daily commute.
Re: capital allowances, I am still confused.
The possible sequence of events that is likely to happen is as follows:
1. I will buy a new car in Sep/ Oct 2015 which I will solely use for the daily commute between my home and a fixed base. I saw on the HMRC website that if the vehicle purchased is new and has CO2 emissions of less than 75g/ km then 100% of the purchase price can be claimed as a first year allowance.
2. In Jan 2016, it is possible that I will become a full time employee of the company for whom I will be consulting in the period 1 Sep 2015 to 31 Dec 2015. If this were to happen, on 31st Dec 2015 I would contact HMRC to inform them of my change in status from sole trader to employee.
3. From 1st Jan 2016 onwards, I would continue to use the vehicle for my daily commute between my home and the same fixed base, it would not be sold and therefore there would be no concept of a "net cost" of the asset.
So, using the data in the example that you provided:
1. If I bought the new car in Sep/Oct 2015 for £10,000, if it had CO2 emissions of less than 75g/ km and if it were solely used for my commute, could I claim a first year allowance of £10,000?
2. If my employment status then changed on 1st Jan 2016 from sole trader to employee but if I continued to use the car for my daily commute, would this change or affect in any way the first year allowance claim of £10,000 that I had made during the 4 month period of being a sole trader?