Place of supply
The location a supply is treated as made in under GST. It decides whether you charge CGST and SGST or IGST.
Place of supply is a legal test, not an address field. Once you know it, the tax treatment follows automatically: same state as the supplier means CGST and SGST, a different state means IGST.
The general rule for goods
Where the movement of the goods ends for delivery to the buyer. If there is no movement, it is where the goods are at the time of delivery. There are special rules for bill-to ship-to arrangements, goods assembled at site, and supplies on board a vessel or aircraft.
The billing address trap
A customer's registered office and their delivery godown are often in different states. The invoice carries both, but only one of them decides the tax. Get this wrong and you charge the wrong tax on every order for that customer until someone notices.
Bill-to ship-to
When A bills B and ships to C, the rules decide the place of supply for the first leg by reference to the third party. Distributors handling drop shipments hit this constantly. It is worth confirming your treatment once with your tax advisor and then applying it consistently.
How KillStock handles it
The place of supply on a sale drives the tax split on the printed invoice and the way the supply appears in the GST summary and returns reports, so the components are decided once rather than judged document by document.
A common mistake
Setting the place of supply on the customer record and never revisiting it when the customer opens a godown in a new state.