12. During the period beginning with 1st December and ending on 31st January in a financial year, a billing authority must notify the Agency of its relevant council tax base if—
(a)before the beginning of that period, the Agency informed the billing authority or, if the billing authority is in the area of a precepting authority, the precepting authority in writing that it will issue a levy to the billing authority or precepting authority for the next financial year; or
(b)the billing authority or, if the billing authority is in the area of a precepting authority, the precepting authority anticipates that the Agency will issue a levy to it for the next financial year.