HMRC doesn't recognise my NI numberI tried to register for self assessment, and it asked to check my identity (to enter my full name, DOB, and my NI number). However after I entered these details, it returned: Unable to verify your identity Sorry, there is a problem with the service Try again later. I have the NI number on the payslip from my previous job, so this cannot be wrong. I have tried multiple times, same result. I also tried "forgot NI number" and it asked me to enter my postcode, but same result as well. I have not changed address since I got my NI number. Before this, I already verified myself using GOV.UK Verify (uploaded passport, driving license etc). Is there anything else I can do? Or who should I contact to address this issue?