a valid NHS tax credit exemption certificate – if you don't have a certificate, you can show your award notice; you qualify if you get Child Tax Credits, Working Tax Credits with a disability element (or both), and have an income for tax credit purposes of £15,276 or less
a valid HC2 certificate
People named on an NHS certificate for partial help with health costs (HC3) may also get help.
You won't be exempt from paying because you receive Incapacity Benefit, contribution-based Employment and Support Allowance, contribution-based Jobseeker's Allowance, Disability Living Allowance, Council Tax Benefit, Housing Benefit or Pension Credit Savings Credit, when paid on their own. Medical conditions don't exempt patients from payment for dental treatment. You'll be asked to show your dentist written proof that you don't have to pay for all or part of your NHS treatment. You will also be asked to sign a form to confirm that you don't have to pay.
You must bring proof of benefit entitlement with you to each appointment.