Pennsylvania Statutes Title 43 P.S. Labor § 912.4. Reimbursement payments

(a) At the end of each calendar quarter or at the end of any other period as determined by the department, the department shall bill each political subdivision of the Commonwealth or any instrumentality of any one or more thereof (or group of political entities) which has elected to make payments in lieu of contributions for the amount of benefits charged to its account during such quarter or other prescribed period that is attributable to service in the employ of such organization.

(b) Payment of any bill rendered under subsection (a) shall be made not later than thirty days after such bill was mailed to the last known address of the political subdivision or any instrumentality of any one or more thereof, or was otherwise delivered to it, unless there has been an application for review and redetermination under section 301.  1

(c) Past due payments of amounts in lieu of contributions, or reports with respect thereto, shall be subject to the same interest and penalties that, pursuant to section 308  2 apply to past due contributions and section 206  3 apply to past due reports.