law: The Integrated Goods and Services Tax Act, 2017
  Chapter IV
  Determination of Nature of Supply
  7. Inter-State supply.-
  (1) Subject to the provisions of section 10, supply of goods, where the location of the supplier and the place of supply are in-
  (a) two different States;
  (b) two different Union territories; or
  (c) a State and a Union territory, shall be treated as a supply of goods in the course of inter-State trade or commerce.
  (2) Supply of goods imported into the territory of India, till they cross the customs frontiers of India, shall be treated to be a supply of goods in the course of inter-State trade or commerce.
  (3) Subject to the provisions of section 12, supply of services, where the location of the supplier and the place of supply are in-
  (a) two different States;
  (b) two different Union territories; or
  (c) a State and a Union territory, shall be treated as a supply of services in the course of inter-State trade or commerce.
  (4) Supply of services imported into the territory of India shall be treated to be a supply of services in the course of inter-State trade or commerce.
  (5) Supply of goods or services or both,-
  (a) when the supplier is located in India and the place of supply is outside India;
  (b) to or by a Special Economic Zone developer or a Special Economic Zone unit; or
  (c) in the taxable territory, not being an intra-State supply and not covered elsewhere in this section, shall be treated to be a supply of goods or services or both in the course of inter-State trade or commerce.