(1) Every S corporation that has Montana source income must file a Form CLT-4S, Montana S Corporation and Composite Information Return, on or before the 15th day of the third month following the close of its annual accounting period.

(2) A six-month extension of time to file an S corporation return is automatically allowed if any tax, penalties, and interest due are paid on or before the date the return is filed.

(3) An S corporation required to file a Montana S corporation information return is subject to a late filing penalty if:

(a) the Montana S corporation information return is not filed by the due date (including extensions);

(b) a copy of the S corporation's federal return is not filed with the Montana S corporation information return; or

(c) a return is filed that does not include the following information:

(i) name, address, and social security or federal identification number of each shareholder;

(ii) the S corporation's Montana source income;

(iii) each shareholder's pro rata share of separately and nonseparately stated Montana source income, gain, loss, deduction, or credit, or item of income, gain, loss, deduction, or credit; and

(iv) each shareholder's pro rata share of separately and nonseparately stated income, gain, loss, deduction, or credit, or item of income, gain, loss, deduction, or credit from all sources.