4. A person shall not use for trade a meter measuring system unless—
(a)it is compliant with the essential requirements other than the provisions relating to maximum permissible errors referred to in paragraph 16 of Schedule 1 to the 2006 Regulations;
(b)it has been erected and installed so as to facilitate testing;
(c)it operates within the maximum permissible errors set out in regulation 5; and
(d)the requirements of regulations 6 and 7 are complied with.