(a) Before the 16th day of each month, each participating municipality shall pay or cause to be paid to the retirement system at the system's office expense contributions in accordance with Section 855.404, current service contributions in accordance with Section 855.405, and prior service contributions in accordance with Section 855.406.
(b) Unless otherwise provided for and paid by a municipality, a municipality shall pay its contributions to the retirement system from:
(1) the fund from which earnings are paid to members; or
(2) the general fund of the municipality.