What expenses are liable to national insurance contributions?
Expenses paid to you by the employer which are in excess of the actual cost will count as gross earnings for the purposes of calculating national insurance contributions. If the inclusion of such expenses takes your gross earnings above the upper earnings limit, you will not pay extra national insurance contributions, but you are still liable to income tax. Examples include travelling and subsistence expenses and mileage allowances. Reimbursement of actual costs and the payment of mileage allowances, within the Inland Revenue authorised limits will be exempt from the figure for calculating national insurance contributions.