Place of supply rules determine GST jurisdiction and whether intra state or inter state tax applies for goods transactions. Section 10 of the IGST Act prescribes five rules for determining the place of supply of goods in domestic transactions: movement-based supplies (place where movement terminates), bill to ship to arrangements (principal place of business of the directing third party), supplies without movement (location of goods at delivery), goods assembled or installed at site (site location), and goods supplied on board a conveyance (place where goods are taken on board). Supplies to unregistered persons use invoice address or supplier location if absent; residual cases fall under Section 10(2).