Md. Code, State Pers. & Pens. § 22-305

(a) A member may purchase service credit as provided in this section for periods of employment described in subsection (c) or (d) of this section for which the member is not otherwise entitled to service credit. (b) (1) A member who purchases service credit under this section shall: (i) complete a claim for the service credit and file it with the Board of Trustees on a form that the Board of Trustees provides; and (ii) pay to the Board of Trustees an amount equal to the annuity reserve and pension reserve required to fund the additional allowance. (2) Except as provided in paragraphs (3) and (4) of this subsection, the member shall pay for service credit purchased under this section at retirement. (3) The surviving spouse of a member of the Teachers’ Retirement System may pay for the appropriate final adjustment under paragraph (3) of this subsection if: (i) the member dies while employed as a member; (ii) the member was purchasing service credit through a payroll deduction; and (iii) the service credit qualifies for benefits under § 29-205 of this article. (c) A member of the Employees’ Retirement System may purchase service credit for a period of employment: (1) not exceeding 10 years of out-of-state public school teaching service; (2) not exceeding 10 years for public or nonpublic school teaching service; (3) not exceeding 5 years for postsecondary school teaching service; (4) not exceeding 10 years of federal service or out-of-state service with a political subdivision; or (5) as an employee of a political subdivision of the State if: (i) the member is not otherwise entitled to receive service credit for the same period under this Division II; (ii) the member is not receiving retirement benefits from a political subdivision of the State for the same period; and (iii) the member, the political subdivision, or both, pay the amount required under subsection (b)(1) of this section. (d) A member of the Teachers’ Retirement System may purchase service credit for a period of employment: (1) not exceeding 10 years of out-of-state public school teaching service; (2) not exceeding 10 years of public or nonpublic school teaching service; (3) not exceeding 5 years of postsecondary school teaching service; (4) on or before December 31, 1970, with Baltimore City as a teacher on a verified leave of absence not exceeding 2 years that is similar in all respects to leaves of absence approved by the Board of Trustees; (5) not exceeding 10 years of federal or out-of-state municipal service; or (6) employment as an employee of a municipal corporation of the State if the member is not otherwise entitled to receive service credit under this Division II.