Although it does not happen too often, there can be cases where an individual treated as an employed earner is actually self-employed, but there is a greater number of cases where a self-employed individual is recategorised as an employed earner. In an ideal world the change would take place from a current date and past periods would be ignored. Whilst the ideal outcome is achieved some of the time, there are also cases where HMRC seeks to collect arrears of Class 1 NIC and where employees and employers seek to recover the overpaid primary and secondary NIC. Much will depend on the amounts involved and the administration involved in rectifying matters.