Will come down to company policy
HMRC says:
So basically no guidance from HMRC, it will be between you and employer to come up with an acceptable means of working out the cost of the electric used by the employee to charge the car.
Whilst excluding electricity from the definition of
fuel can cause administrative problems regarding the reimbursement of business mileage, there are some benefits. In particular, s149(4) ITEPA 2003 extends the exclusion from the car fuel charge to any ‘
facility or means for supplying electrical energy’. This means that an employer can, for example, pay for the following without a taxable benefit arising:
- A vehicle charging point to be installed at the employee’s home.
- A charge card to allow individuals access to commercial or local authority charging points.
Risk with a flat rate charge like 18p per kW charged like Russinating suggested is that if that is more than the employees cost then the employee may be subject to tax on the extra. Conversely if it isnt enough, although the employee will be able to claim tax relief on the difference they will still be out of pocket.