Car and mileage £'s through Company used in CSA1 assessment

ScotNess_2

If someone is on CSA1 and uses a car as part of their work ie someone like a Home Care Assistant working for an agency and claims the petrol money via their salary, does this get included in the figures used as net income or is it looked at carefully and excluded considering it is only a repayment for money already paid out by the employee in order for them to undertake their job role and is for mileage above an beyond just driving to and from their usual place of work base and the amount allowed approved by the government set figures allows a little extra on top for wear and tear for use of their own vehicle.

Do the same rules apply for NRP and PWC or is a PWC allowed the extra money on their income but not the NRP as seems to be the standard ruling with the biased CSA.

Also what happens if I was to get a leasehold car through my salary, therefore reducing my net income, do the CSA see that on my payslips and add the amount back to my gross/net income to include it in my salary figures for calculating CSA Maintenance assessment.

Is that the same ruling also for PWC?

I have an old banger that is due it's MOT soon and is bound to fail it, however I have the chance to join a leasehold scheme as part of a salary sacrifice scheme I can join but wondered about the implications of it on the CSA assessment on CSA1