M-Form Filing Extended Due Date

March 25, 2021

To: Manufacturers, Real Estate Owners and Preparers


  • Disregard this reminder if you already filed or requested an extension to file your 2021 M-Forms
  • Annual filing of M-Forms is a statutory requirement for all state-assessed manufacturers

IMPORTANT – Note to Recipient

Your email address is associated with the manufacturing account identified in the subject line as an authorized user within the Wisconsin Department of Revenue's (DOR) Manufacturing Assessment System (MAS).

Take action - if you are the:

April 1 – Extended Filing Deadline (2021 Forms M-L, M-P, M-R)

We would like to remind state-assessed manufacturing property owners who requested an extension to file 2021 Manufacturing Property Returns (M-Forms) of the upcoming April 1 extended due date.

Late Filing Penalty

If you do not file your M-Form or file it late, you will receive a non-filing penalty and lose the right to appeal your assessment. See Late filing penalty.


To avoid a delayed response, contact the district office in your area.