Voluntary Class 2 NI is generally paid by people who are self-employed but do not exceed the small profits threshold. For just £3.15 per week, you can preserve your entitlement to state benefits and the state pension if you fall into this category - far more efficient than paying Class 3 NI at £15.85. However, there has been an issue with some 2020/21 tax returns rejecting the voluntary NI entry. At the time the returns were filed, HMRC extended the filing deadline to the end of February 2022 due to the pandemic. Only the tax returns filed after the usual deadline of 31 January 2022 are affected and an error message is displayed explaining that it is too late to pay voluntary NI. This could mean that the voluntary NI was either not paid, or it was paid and your self-assessment account is simply sitting with an unallocated credit for the amount.

HMRC will be writing to everyone in December to explain how this can be resolved. If this affects you but you do not receive a letter from HMRC you can call the National Insurance Helpline on 0300 200 3500. It's worth checking whether you already have enough qualifying years for the state pension before making a further payment to HMRC. You can check your NI record in your personal tax account.