Amalgamation liability: intercompany supplies during retrospective effective periods are included in turnover and taxable. When a merger order takes effect from an earlier date, supplies of goods or services between the merging companies occurring between the order's effective date and the order date are included in each company's turnover and liable to tax; notwithstanding the merger order, the companies are treated as distinct for the period up to the order date and their registration certificates are cancelled with effect from the order date.