Landlords paying voluntary Class 2 National Insurance contributions

Dear HMRC, Hope you are doing well. The website (https://www.gov.uk/renting-out-a-property/paying-tax) states that landlords can pay voluntary Class 2 National Insurance contributions if any of the following apply: - Being a landlord is your main job - You rent out more than one property - You’re buying new properties to rent out I have had my UTR number for the online self-assessment for the past few years. Could you please advise me on how to register for the aforementioned Class 2 NI contributions? Thank you so much! Kind Regards, Mike

Hi I have the same problem please let me know if you get an answer thanks Calvin

Hi Mike,
To register for Class 2 National Insurance you can either contact our helpline or webchat.
Please find our contact details below: 
Number  0300 200 3500
Text Relay  18001 0300 200 3500 (Text Relay)
Overseas  +44 191 203 7010
Open  Monday to Friday: 8am to 6pm
Closed on Saturdays, Sundays and Bank Holidays.
Web Address
National Insurance: detailed information
Thank you.