Value of supply rules define transaction value and required inclusions for GST valuation, with specific discount and related party tests. Determination of the value of a taxable supply is based on the transaction value where supplier and recipient are not related and price is sole consideration; the value must include non-GST taxes charged separately, amounts paid by the recipient on supplier's behalf, incidental expenses (including commission and packing), charges for acts done by the supplier at or before delivery, interest or late payment penalties, and subsidies directly linked to the price. Discounts recorded on invoice or contractually established post-supply with reversal of input tax credit are excluded. Prescribed methods apply where transaction value cannot be determined and notified supplies may be valued as prescribed. Related persons are broadly defined.