53 Pa.C.S. § 8404

If a municipality and school district both impose an earned income and net profits tax on the same individual under the Local Tax Enabling Act and the municipality and school district are limited to or have agreed upon a division of the tax rate in accordance with section 8 of the Local Tax Enabling Act, then the municipality that continues to levy the earned income and net profits tax under the Local Tax Enabling Act shall remain subject to that limitation or agreement in the event that the school district opts to impose an earned income and net profits tax under section 8711 (relating to earned income and net profits tax).