SECTION 5(4) OF IGST ACT 2017.

SECTION 5(4) of IGST Act, 2017 says:
"The integrated 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 and all the provisions of this Act shall apply to such recipient as if he is the person liable for paying the tax in relation to the supply of such goods or services or both."
After a close perusal of this Section we can infer that this Section is made in order to bring interstate supplies emanating from URD to a registered person under RCM.

Section 24 (i) of CGST Act provides for compulsory registration of a person who is making any interstate taxable supply. Reading through both Sections we can understand that even though Section 24(i) of CGST Act provides for a compulsory registration for such supplier, still Section 5(4) of IGST Act tries to bring unlawful interstate taxable supplies under tax net. This is understandable.
Two types of unlawful interstate taxable supplies can happen under GST:
1. From URD to registered person,
2. From Composition dealer to registered person.
Looking at these two unlawful interstate taxable supplies two questions arise:
1. The receiver of interstate supplies shall pay tax under RCM. But what about the unregistered supplier? Doesn't this Section remain silent on penal action on activity by the unregistered supplier? Doesn't this Section inspire such interstate supplies as long as the recipient is paying tax under RCM? Shall Section 125 of CGST ACT ( GENERAL PENALTY) be attracted on part of the unregistered supplier?
2. Doesn't Section 5(4) of IGST ACT remain silent on RCM chargeability on interstate taxable supplies emanating from a Composition dealer registered u/s 10 to a registered person? Who will pay tax under RCM for such taxable interstate supplies? Definitely not the Composition dealer! If the receiver of such supplies shall pay tax under RCM the IGST Act doesn't specifically have provision to say that !
In my opinion Section 5(4) of IGST Act shall be modified to include the Composition dealer as well. And also the reference shall be made as for the Section providing for penal action on such suppliers.