RE: NI Class 3 voluntary contribution 18 digit reference numberForget phoning, do it through the Digital Assistant as suggested by RealityCheck. I succeeded that way.
RE: NI Class 3 voluntary contribution 18 digit reference numberSame problem, had to give up after an hour. I wondered if I could use my reference from last year or if they issue a new one. If anyone from HMRC reads this, it would be really helpful if they could clarify this. And if I can use my reference from last year, it would be useful if it appeared in my personal information when I signed in through Government Gateway (it doesn't - although I do actually have a note of it).