CIS subcontractors fuel expenses

in VAT
Hi,
I've recently taken over the bookkeeping for a firm of CIS contractors, who pay CIS subcontractors. Some of the subcontractors claim fuel expenses (i.e for mileage to and from jobs, not for running the machinery etc.). Our accounting package is Xero.
My question is, how should the fuel mileage expenses be entered onto Xero? I'm thinking it should not be included under the CIS subaccounts, but should be entered as vehicle expenses with VAT?
Can anyone please advise if my thinking is correct, or if not, please let me know the correct way.
Many thanks,
Kirstie
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