(a) Mandatory contributions.--A participant shall make mandatory pickup participant contributions through payroll deductions to the participant's individual investment account for school service required to be credited in the plan. The employer shall cause those contributions for service required to be credited in the plan to be made and deducted from each payroll or on such schedule as established by the board.

(b) Voluntary contributions.--A participant may make voluntary contributions through payroll deductions, through direct trustee-to-trustee transfers or through transfers of money received in an eligible rollover into the trust to the extent allowed by IRC § 402. Rollovers shall be made in a form and manner as determined by the board, shall be credited to the participant's individual investment account and shall be separately accounted for by the board.

(c) Prohibition on contributions.--No contributions shall be allowed that would cause a violation of the limitations related to contributions applicable to governmental plans contained in IRC § 415 or in other provisions of law. In the event that any disallowed contributions are made, any participant contributions in excess of the limitations and investment earnings on those contributions, minus investment fees and charges, shall be refunded to the participant by the board.