According to the Wisconsin instructions, you are suppose to attach a copy of your Federal return when you are mailing in your return.
5. Federal Return – A complete copy of your federal return (Form 1040) and its supporting schedules and forms (such as federal
Form 8886, Reportable Transaction Disclosure Statement.)
See page 5 of the instructions for filing your state return
https://www.revenue.wi.gov/TaxForms2017through2019/2018-Form1-inst.pdf
