(1) Where a local authority passes the resolution referred to in section 20(2), it shall notify the Revenue Commissioners of the percentage by which the basic rate is to be varied, and -

(a) the notification shall be sent to the Revenue Commissioners in the form and manner specified by them, and

(b) the notification referred to in paragraph (a) shall be sent to the Revenue Commissioners in the year in which the resolution is passed, on or before -

(i) in a year in which a valuation date occurs, 31 August in that year, and

(ii) in any other year, 15 October in that year.

(2) Where a local authority complies with subsection (1), the varied rate shall take effect from the liability date in the year in which the notification is sent to the Revenue Commissioners.