You must give P11D forms to HMRC by 6 July following the end of the tax year.
So for example, for the tax year 2017 to 2018 the P11D forms had to be returned to HMRC by 6 July 2018.
If you don’t submit the correct forms and on time, HMRC can impose a penalty of £100 per 50 employees for each month (or part of a month) that your P11D(b) is late.