It can take a month or two for your online record to be updated. Tip: give HMRC a ring a couple of weeks after paying your NIC to check payment has been credited to your account. When it comes to the HMRC voice-activated "in a few words tell us why you have rung us today" say nothing. Keep saying nothing to any further questions until the one about "is it you you are ringing about" ( or something like that). Say "yes" and you will get straight through to an HMRC advisor.