NIM05703 | Class 1 NICs: Expenses and Allowances: Mileage allowances: Class of NICs due
From HM Revenue & Customs · National Insurance Manual
If an employer
reimburses an employee the costs of using their own car for business travel, either by way of a mileage allowance or by exact reimbursement:
see NIM05708 for payments made before 6 April 2002
provides fuel and meets other costs directly, for example by supplying fuel from the employer’s own fuel pump or by contracting direct with a garage for servicing and repairs, Class 1A NICs may be due, see NIM05660.