15.—(1) Subject to regulation 16, an undertaking is a “relevant undertaking” in relation to a compliance period if, on the qualification date for that compliance period, it is—
(a)a large undertaking, or
(b)a small or medium undertaking which is a group undertaking in respect of a relevant undertaking falling within sub-paragraph (a).
(2) For the purposes of these Regulations whether an undertaking is a large undertaking, or is a small or medium undertaking, is to be determined in accordance with Schedule 1.