For reasons lost in the mists of time, self-employed individuals pay two types of national insurance contributions (NIC): Class 2 and Class 4.
Class 2 is charged at £148.20 per year (for 2017-18), and is only payable if your annual profits are £6,025 or more. Class 4 NIC is calculated as 9% of your profits up to £45,000, plus 2% of profits above that threshold, but you pay it only if your annual profits are £8,164 or more.
Class 2 NIC provides a year’s credit towards the state pension and entitlement to certain other state benefits; Class 4 NIC provides you with no credits or entitlements at all.
The Government had planned to combine Classes 2 and 4 NIC from 6 April 2018 and to attach the entitlement rights to the combined NIC charge. This would simplify NIC for self-employed people. However, those with very small profits would no longer be able to pay the low level of Class 2 NIC on a voluntary basis to secure state benefit entitlements for a year.
The Government has now decided to postpone the NIC merger until 6 April 2019. This means that you will carry on paying Class 2 and Class 4 NIC for 2018-19 through your self-assessment tax bill as now.
