Voluntary NI contributions: backpay whilst overseas

My wife and I just received our NI contributions letter for backpaying whilst overseas. We submitted the same details as we have worked overseas at the same places, for the same duration etc.. My wife was assessed as needing to pay class 2 but I was assessed as needing to pay class 3. Can I appeal this decision with additional supporting documents? We applied online in July and received the letter today. Thanks for any suggestions for the way forward. (We both worked for over 3 years before working abroad).

Hi william,
Thank you for your query.
You can complete a new CF83 application providing supporting documents. You should also provide a covering letter asking for your application to be looked at again, and explain why you think that you meet the criteria to pay at the Class 2 rate. The application can be found here -
Apply to pay voluntary National Insurance contributions when abroad (CF83) - GOV.UK (www.gov.uk).
Thank you.