logatex

I sent my CF83 last week [9 May 2023] by registered mail - a couple of questions 1) Does someone sign on receipt of registered mail, so I'll know (via Royal Mail) if it's been received? 2) Can I confirm that the important thing is for my CF83 to be in the system by 31 July 2023 in order to make N back-payments from 2006-2017? In other words, that it won't matter - due to the backlog - that my case, and the decision on class 2 or 3 contributions - will probaby not be dealt with until early next year, and thus my payments will not be made until then