3.—(1) A relevant charging authority is, or relevant charging authorities are, liable to pay to the Secretary of State a fee—
(a)in the circumstances set out in paragraph (2), and
(b)of the amount specified in paragraph (3).
(2) The circumstances are when—
(a)a person pays one or more charges in relation to the charging scheme made by the relevant charging authority or relevant charging authorities (as the case may be) by a payment processed by the clean air zones central services (a “processed payment”);
(b)the processed payment is made in the period starting on 1st January 2021 and ending at the end of 31st March 2027.
(3) The amount is, in relation to a processed payment, £2 per charge covered by the processed payment.
(4) Liabilities under paragraph (1)—
(a)are payable on invoice by the Secretary of State,
(b)are recoverable as civil debts, and
(c)in respect of relevant charging authorities, are to be treated as joint and several liabilities.