4. Where the Organisation establishes to the satisfaction of the Revenue Commissioners that, in connection with its official activities it has borne tax on the delivery to it of goods or on the rendering to it of services, and those goods or services are of substantial value, and fulfils to the satisfaction of the said Commissioners all the conditions which are specified in paragraph 5 of this Order it shall be entitled to be repaid the tax so established as having been borne or paid.