Hi Emma Jane,
You can find the criteria for paying Voluntary Contributions abroad by reading NI38 on the gov.uk website
Social Security abroad: NI38
If you believe you are eligible, you’ll then have to apply using the form CF83 ‘Application to pay National Insurance Contributions abroad’
Apply to pay voluntary National Insurance contributions when abroad (CF83)
This can be completed online or by print and post.
Once we receive your application our caseworkers will be able to investigate your circumstances to see if you are eligible for making payments.
Your husband will need to do the same.
Thank you.