If you would like to pay voluntary contributions to increase your state pension you can find more information here:
Pay voluntary Class 3 National Insurance
For UK residents, the first thing you will need to do is to contact DWP.
The reason we require you to contact DWP is because they will be able to advise you what years it is best for you to pay, and if you will benefit from paying them. Although these contributions are voluntary they cannot be refunded if paid incorrectly, therefore you should ensure that you will benefit from making the payment.
If you are below pension age you should contact future pension centre on 0800 731 0175
If you are over pension age you should contact the pension service on 0800 731 7898
DWP phone lines are open between 8am and 6pm
Once you have this information you should contact HMRC to obtain an 18 digit reference number.
You can then use this number to pay online, at your bank, or via online banking
The contact number for HMRC is 0300 2003500 (lines are open between 8am and 6pm)
HMRC will accept your original date of contact, and the date the payment is received will be honoured, however it may take up to 8 weeks for your national insurance record to be updated.
For customers who reside overseas you will need to read the booklet NI38, and complete the CF83, making sure you tick the option that you would like to know what arrears you can pay.