This provision outlines the hierarchical methodology for determining the market value of a supply of goods or services for VAT purposes. It defines 'Similar Supply' as a comparable supply in characteristics, quality, and reputation. The primary method establishes market value as the cash consideration a supply would achieve between unrelated parties in the State. If this cannot be determined, the value of a similar supply is used. As a final measure, the market value is determined by the replacement cost of identical goods or services, ensuring the valuation is at arm's length for accurate tax calculation.