(a) Each employer whose account has been chargeable with benefits throughout four or more consecutive calendar quarters shall pay contributions at the rate prescribed by the table in Section 204.042 or a table extended under Section 204.043.
(b) Except as provided by Subsection (c), a change in the rate applicable to an employer takes effect on January 1.

(c) The rate for an employer who becomes subject to contributions under Subsection (a) for the first time at the close of a calendar quarter takes effect on the first day of the next calendar quarter and continues in effect until the January 1 of the next calendar year.