Employer won't submit P11D forms

My old employer won't submit the P11D forms for 23/24 tax year. They have gone into administration and won't provide the information that is needed for my self-assessment tax return. What's the best course of action here?

I want to add that this is going to have a knock-on effect on my tax return in that I would be under-reporting and under-paying tax because I don't know the total cost of benefits provided.

Hi,
Unfortunately we are unable to check your record to see what P11D information we may hold via the forum, you would need to contact HMRC.
Income Tax: general enquiries
Thank you.