S Corporation Due Dates
You must file Form M8, S Corporation Return and pay the tax owed by the due date for filing your federal return.
Generally, this is March 15 of the following year.
If you file on a fiscal year basis, it's the 15th day of the third month following your tax year.
The filing date is the U.S. postmark date, or the date recorded or marked by a designated delivery service. Postage meter marks are not valid. When a return is considered late, the date it is received at the Minnesota Department of Revenue is treated as the date filed.
When the due date falls on a weekend or legal holiday, returns and payments that are postmarked or electronically transmitted on the next business day are considered on time.