S Corporations in Montana


S corporations are corporations that elect to pass corporate income, losses, deductions, and credits through to their shareholders for federal tax purposes.

See S Corporations on IRS.gov for more information on the Small Business Corporation Election.

S corporations in Montana must file an annual Montana Pass-Through Entity Tax Return (Form PTE).

Due Dates and Extensions

Montana S corporation returns are due at the same time as your federal Form 1120S:

Calendar Year
March 15
Fiscal Year
The 15th day of the third month following the close of the S corporation's tax year.
Example: If your S corporation's tax year ends on March 31, your return is due on June 15.

If a due date falls on a weekend or holiday, it is due on the next business day.

Pass-through entity tax, pass-through withholding and composite taxes are due on the original due date of the Form CLT-4S.

Extension Deadlines

Montana grants all S corporations an automatic six-month extension to file a return. This means returns filed on extension are due:

Calendar Year
September 15
Fiscal Year
The 15th day of the ninth month following the fiscal year end.
Example: If your S corporation's tax year ends on March 31, your return is due on December 15.

Extension deadlines are for returns only.

Any tax liability must still be paid by the original due date or it will be subject to uniform penalties and interest.