Nanny and Private use of Car
If you have provided nanny with private use of a car, you need to inform HMRC straightaway. The quickest way is to complete a form P46 car
By notifying them straightaway, they will reduce nanny’s tax code the month she is given the car.
Failure to tell them when she has the car, will mean her tax code will be coded incorrectly causing an under payment.
Even though you have notified HMRC of the car via a P46 car, you will need to complete a P11d and pay Class 1A National Insurance on the benefit amount.
Please see link below