Place of Supply rules determine tax characterisation under GST, directing IGST or CGST+SGST liability and preserving ITC integrity. Determination of the place of supply under GST, based on the destination principle, decides whether a supply is inter State or intra State and thus whether IGST or CGST plus SGST applies. Chapter V of the IGST Act prescribes general and specific rules for goods and services, with separate treatment for domestic and cross border transactions and distinctions between B2B and B2C supplies; location of the supplier and place of supply are the key tests. Cross utilisation rules permit IGST credit to be used for IGST, CGST and SGST and CGST/SGST credit to be used for IGST.