If you purchase software, your vendor can verify that its forms' designs have been approved. If you develop your own software, obtain approval from the department for all substitute forms created within your application. A complete Form 1, 1A, WI-Z, 1NPR, 1X, or Form 2. Copies of other state tax returns and withholding statements. A copy of the federal extension of time to file, when applicable, is the last document attached to the return.
Mail returns to the proper post office box.
The addresses are printed on the forms. Sending returns to the wrong post office box delays refunds.