I left the UK for good about 2.5 years ago. Neither before I left nor after I haven't filed P85 or otherwise informed HMRC about my departure. However I was not working and was not obliged to file Self-Assessment in the tax year and the tax year before I left the country. My last Self-Assessment was submited 2-3 years before I decided to leave, after that it was closed. So I didn't owe anything as well as I didn't expect any refunds.
Was P85 a mandatory form to submit in my case? If yes, are there any penalties or other consequences for its late submission? If it is not mandatory, is it worh submitting it after more than 2 years, taking into account that I might be planning to return to the UK sometime in future?