FEIN stands for Federal Employer Identification Number. Businesses apply for this number with the US IRS during initial business registration with the State. It is used for tax and identification purposes.
If you do not know the FEIN for your business, reach out to your accounting department to see if they have the number on file. They should have this information. If you/your accounting department does not have this number in your records, please reach out to the Wisconsin Department of Revenue staff directly for assistance. You can contact them by phone by at (608) 266-2776.