Value of supply inclusive of GST: use back-calculation to extract the tax component from inclusive prices for invoicing and valuation. Determination of the value of supply inclusive of GST requires back-calculation: multiply the price inclusive of taxes by the applicable tax rate and divide by the sum of one hundred plus the applicable tax rates. This method applies to MRP inclusive of tax and to cash discounts or interest recovered inclusive of tax. Open market value excludes taxes and reflects the full monetary value in transactions between unrelated parties, while supplies of like kind and quality are those that closely resemble the supply being valued in characteristics and reputation.