Health care services by a clinical establishment, an authorised medical practitioner or para-medics have been exempted from GST.
This means that a doctor falls under exempted category and he need not be a 'registered person' under GST Act
Further sub section 4 of Section 9 of the CGST Act says that , " the central tax in respect of the supply of taxable goods or services or both by a supplier, who is not registered, to a registered person shall be paid by such person on reverse charge basis as the recipient .......".
Thus it is clear that the burden to pay tax under RCM arises only if the recipient is a registered person. So purchasing from an URD doesnot make the Doctor liable under RCM as he is not a registered person under the Act. Nature of supply whether it is exempted or not is insignificant.