HMRC moved the collection of Class 2 National Insurance to the Self Assessment system (via the tax return) in 2015/16.
The yearly Class 2 contributions are as follows:
These can be paid voluntarily if your profits are below the contribution threshold (2018/19 £6,205 & 2019/20 £6,365). However, if you do not pay your tax bill by the Self Assessment deadline (31st January), you will need to ring up the National Insurance helpline (0300 200 3500) and pay the amount to them directly.
You can check your contributions to your State Pension by:
~ Setting up/logging into your Personal Tax Account via the link below
~ Contacting the Future Pension Centre on 0800 731 0175