Hi, I was in the same position, calling since February, sent two forms via registered post, sent 2 messages online, (which I now can't find again, maybe removed). They did acknowledge in april/May that they had received the messages via the website, log into https://www.access.service.gov.uk/login/signin/creds for your own account and on the top menu they have check. But what was worrying me was I couldn't remember what they said and there was no record of the two forms sent. - even though sent registered they got no signature - around the time of the strikes. So at a loss I called the suggested above from HRMC5 - National Insurance: general enquiries link, and I got through. A really nice man helped me and did state the same above - Please note they cannot advise you if you should pay the shortfall but could tell me they had recieved the forms - both of them and the processing time is 39 weeks from the date of recieving them, for me, and they would honour the fact theyrecieved them before the cut off date, which is now July 31st. I also was lucky enough that he could put me through to the right people who confirmed everything he had said. Even though it will be a while before sorting it out I have peace of mind - thanks HMRC Admin 5 I can sleep.