A self-employed individual filed self-assessment returns for several years and should be eligible to make voluntary Class 2 NICs. The business profits were always below the threshold for compulsory NICs so no contributions were made at the time.
HMRC is fully aware of the existence of the business and would have automatically demanded NICs if the profits ever exceeded the threshold. However, the taxpayer's request to pay Class 2 NICs voluntarily has been rejected 'because not registered with the NIO as self employed during these years'. The claim is not time-barred; this is the only reason.
It seems like a perverse outcome, given that the NIO is part of HMRC. Does anyone know how one should 'register' with the NIO if not by notifying the tax office of self-employment, and how the rejection might be challenged?