​Tell your dental practice you want NHS treatment when you make an appointment.
When you arrive for your appointment, you'll be given a form to fill out – if you do not have to pay, put a cross in the appropriate box. 
If you have a valid HC2 certificate or tax credit exemption certificate, write in the certificate number.
If you have a valid HC3 certificate, write in the certificate number and the maximum your certificate says you can pay. You will pay either what appears on the certificate or the actual charge, whichever is the least.
Dentists are not responsible for advising patients on exemptions, and it's the patient's responsibility to know if they are exempt.
You will need to show proof of your entitlement to help with dental costs. If you are not sure whether you are entitled to help, you must pay. You can claim a refund, but make sure you keep all receipts.