The Pennsylvania Supplement to Form U-1 is a form developed by the Internal Revenue Service (IRS) for employers in Pennsylvania to report wage and withholding information for their employees. It is used to report wages and taxes withheld from an employee's paycheck, such as state and local taxes, Social Security, Medicare, and other withholding. It is also used for filing federal unemployment tax reports. This form is usually prepared and filed with the employee's Form W-2, and must be filed with the IRS in order to comply with federal laws. The Pennsylvania Supplement to Form U-1 comes in two different types: the Standard Form U-1 and the Simplified Form U-1. The Standard Form U-1 is used to report wages and withholding for employees in Pennsylvania, while the Simplified Form U-1 is used to report wages and withholding for employees in other states. Both forms must be submitted to the IRS each quarter.