Changing schemes
71. Save as the Commissioners may otherwise allow, a retailer who accounts for VAT on the basis of taxable supplies valued in accordance with any scheme shall, so long as he remains a taxable person, continue to do so for a period of not less than one year from the adoption of that scheme by him, and any change by a retailer from one scheme to another shall be made at the end of any complete year reckoned from the beginning of the prescribed accounting period in which he first adopted the scheme.