P11ds and the P11d(b) form are due by 6 July following the end of the tax year that the benefits were provided and there are penalties for missing this deadline. So the P11d forms for 2017/2018 are due 6 July 2018.
Any additional employers national insurance calculated on the P11d(b) is due for payment by the 22nd July, if paying electronically (19th July if paying by cheque).
What are the Penalties for Missing the P11d Deadline?
Employers will get a penalty of £100 per 50 employees for each month or part month your P11d or P11D(b) forms are late. You’ll also be charged penalties and interest if you’re late paying HMRC.