Ariz. Rev. Stat. § 38-843.01
Each employer shall pick up the contributions required of members on account of compensation paid after the effective date specified in the resolution of the board activating the provisions of this section. The picked up contributions shall be treated as employer contributions for the purpose of tax treatment under the United States internal revenue code. The specified effective date shall not be before the date the system receives notification from the internal revenue service that pursuant to section 414(h) of the internal revenue code the member contributions picked up shall not be included in gross income for income tax purposes until the time that the picked up contributions are distributed by refund or pension payments. The employers shall pick up the member contributions from monies established and available in a retirement deduction account, which monies would otherwise have been designated as member contributions and paid to the system. Member contributions picked up pursuant to this section shall be treated for all other purposes, in the same manner and to the same extent, as member contributions made before the effective date.
A.R.S. § 38-843.01