What is the relationship between voluntary NI contributions and self-assessment tax return ?

I lived and worked in the UK until 2019, then permanently left. For tax years 2019/20, 2020/21 and 2021/22, I continued to receive income in the UK and filed non-resident tax returns. For these years, my NI contributions are full. In 2022/23 though (and for the foreseeable future), I didn't receive any UK income and it appears as a gap in my NI record, Initially I thought I had no reason to continue filling non-resident tax returns, and then I read https://www.gov.uk/self-assessment-tax-returns/who-must-send-a-tax-return. More specifically, under the section "Other reasons for sending a return" it says "pay voluntary National Insurance contributions". Can someone please explain the relationship between the two ? Is this an alternative to submitting CF83 ? Thanks !

Hi,

If you have left the UK permanently and you have no income at all, please contact our Self Assessment team to ensure it can all be closed.

Self Assessment: general enquiries

For National Insurance due to leaving the UK, you now have the option to pay voluntarily by the NI38 and the CF83 application forms that you have mentioned. You will also need to speak to our National Insurance team to ensure you have told us you have left the UK permanently.

National Insurance: general enquiries

Voluntary National Insurance contributions when you live and work in the UK can be paid to top up your National Insurance. When you leave the UK you can also apply to pay voluntary National Insurance but this is overseas National Insurance. If you have left the UK you must pay voluntary National Insurance from abroad by the CF83 application process.

If you still have access to your personal tax account, you can self serve and inform us of your changes and have the option to use webchat services if you have not informed us already.

Thank you.