(1) In this section -

"accounting period" means a period of 3 consecutive months beginning on 1 January, 1 April, 1 July or 1 October;

"'advanced cover" and "non-advanced cover", in relation to a relevant contract, have the same meanings respectively as in section 6A of the Health Insurance Act 1994;

"authorised insurer" means any undertaking (not being a restricted membership undertaking) entered in The Register of Health Benefits Undertakings, lawfully carrying on such business of medical insurance referred to in the definition of "relevant contract" but, in relation to an individual, also means any undertaking (not being a restricted membership undertaking) authorised pursuant to Council Directive No. 73/239/EEC of 24 July 1973 [No. L228, 16.08.1973, p.3], Council Directive No. 88/357/EEC of 22 June 1988 [OJ No. L172, 04.07.1988, p.1], and Council Directive No. 92/49/EEC of 18 June 1992 [OJ No. L228, 11.08.1992, p.1], where such a contract was effected with the individual when the individual was not resident in the State but was resident in another Member State of the European Communities;

"due date", in relation to an accounting period, means the 21st day of the second next month following the end of that accounting period;