Dual levy of GST: CGST and SGST apply together on taxable supplies, with input tax credit restricted to each tax head. CGST and SGST are levied simultaneously on taxable supplies except specified exemptions and threshold exclusions; both taxes use the same transaction value. SGST is chargeable only for intra state supplies while CGST applicability is not conditioned on intra state location. Input tax credit is head specific: CGST credit may be utilised only against CGST liabilities and SGST credit only against SGST liabilities, precluding general cross utilisation.