Any political subdivision of the Commonwealth or any instrumentality of any one or more thereof, which is or becomes subject to this act shall pay contributions on remuneration paid by it for employment under the provisions of section 301 , 301.1, 301.2 or 301.6, as the case may be, unless an election is made to pay on a reimbursement basis as hereinafter provided.
43 P.S. § 912.1