I correctly filed P46(Car) forms via RTI re replacement of a car, but in the tax code issued, HMRC only recognise the car being withdrawn, not the BIK on the new car. Spoke to HMRC, and they say they haven't received/actioned details of new car, and cannot discuss anyway as I'm an agent.
So I filed the form again just showing the new car, but they still have not updated his tax code.
Client advised me to manually calculate his correct tax code and use that instead. But I'm conscious of RTI penalties, and prefer HMRC to get it right.
So I'm coming up to the second month of applying the tax code I calculated.
I've tried to get the employee to speak to them directly, but he doesn't want to.
What is best way to proceed? Continue using the (correct) tax code I calculated, or use the one issued by HMRC, which will generate him a massive PAYE underpayment during 2017/18?