20.—(1) A notice to owner may not be served after the expiry of the period of 6 months beginning with the relevant date.
(2) The relevant date—
(a)in a case where a notice to owner has been cancelled under regulation 23(5)(c) of these Regulations, is the date on which the district judge serves notice in accordance with regulation 23(5)(d);
(b)in case where a notice to owner has been cancelled under regulation 5 of the Representations and Appeals Regulations, is the date of such cancellation;
(c)in a case where payment of the penalty charge was made, or had purportedly been made, before the expiry of the period mentioned in paragraph (1) but the payment or purported payment had been cancelled or withdrawn, is the date on which the enforcement authority is notified that the payment or purported payment has been cancelled or withdrawn;
(d)in any other case, is the date on which the relevant penalty charge notice was served under regulation 9.