Union Grove Office from Main Street Union Grove Office 901 Main Street Union Grove, WI 53182 Phone Number: 262-878-3667 Fax Number: 262-878-3704 Office Hours    Tax Season (January 1st through April 30th) Monday thru Friday: 8:00 AM - 5:00 PM Non-Tax Season (May 1st through December 31st) Monday thru Thursday: 7:30 AM - 5:00 PM Friday: 7:30 AM - Noon