4.—(1) For the purpose of this regulation an “invalid notice” (“hysbysiad annilys”) means a demand notice that does not comply with regulation 3(1).
(2) A requirement to pay amounts contained in an invalid demand notice applies as if the notice was valid if—
(a)the failure to comply with regulation 3(1) was due to a mistake; and
(b)the amounts required to be paid under the invalid demand notice were demanded in accordance with Part II of the Non-Domestic Rating (Collection and Enforcement) (Local Lists) Regulations 1989.
(3) A billing authority must, as soon as practicable after the mistake is discovered, issue to the ratepayer concerned a statement of the matters prescribed in Schedule 1 which were not contained in the invalid notice.