Can I still pay additional NI contributions

I retire in October 2024, up to the fifth of April 2024 I have accumulated 32 years of full National Insurance payments, In the year 2015/2016 I made 47 weeks of NI payments. In the years 2014/2015, and 2013/2014 I made no contributions as I was doing voluntary work in Cambodia. My question is can I pay voluntary contributions In Those Years to make up my full state pension of 35 years. I have checked my pension summary on the government Gateway site and it says that I can make the payments before 5th of April 2025 but I wanted to check whether this was correct and how do I if it is possible make those payments. Thank you for your help

Hi Simonapsey apsey,
Yes the date of April 2025 is correct for deadline to pay voluntary contributions for years older than six years.
For the years working in Cambodia as a volunteer you would need to complete for CF83 from gov.uk and apply to pay voluntary contributions for Development Workers abroad – complete and return the form and our international team will advise what and how you can pay.
For the year 15/16 if this was just in the UK then you can call our National Insurance helpline to get the amount confirmed and a payment reference to allow you to pay via bank transfer or cheque to us.  If this year was also linked to an abroad period, include it in the application form mentioned above.
Thank you.