Who Is Required to File Missouri Corporate Income Tax?

Understanding which entities must file Missouri corporate income tax returns is a common inquiry for businesses operating within the state. This tax applies to the income generated by corporations, and specific criteria determine a company’s obligation to file. This article clarifies the definitions, activities, and requirements for corporate income tax filing in Missouri. It outlines entity types, taxable presence, and applicable exemptions.

Defining a Corporation for Missouri Tax Purposes

Missouri aligns with federal classifications when defining a “corporation” for income tax purposes. C-corporations are subject to the state’s corporate income tax. These entities file Federal Form 1120, and their tax liability is determined at the corporate level. Missouri’s corporate income tax rate is 4 percent for tax years beginning on or after January 1, 2020.

S-corporations are treated as pass-through entities for federal and Missouri income tax purposes. Income and losses pass through to shareholders and are taxed on individual returns, avoiding double taxation. S-corporations must still file an informational return, Form MO-1120S, if they file Federal Form 1120S and have a Missouri resident shareholder or any income from Missouri sources.

Limited Liability Companies (LLCs) are taxed as partnerships by default, or as sole proprietorships if they have a single member. If an LLC elects to be taxed as a corporation for federal income tax purposes by filing IRS Form 2553, Missouri will similarly treat it as a corporation. Such an LLC would be responsible for filing Form MO-1120 and paying corporate income tax on its Missouri-sourced income.

Establishing a Filing Requirement (Nexus)

A corporation’s obligation to file a Missouri corporate income tax return is established when it has “nexus” with the state. Nexus signifies a sufficient connection or presence that permits Missouri to impose its income tax. This includes domestic corporations organized under Missouri law, and foreign corporations licensed to do business or actively “doing business” within the state.

“Doing business” in Missouri extends beyond a physical office or employees. It encompasses deriving income from sources within the state, such as sales, services, or property. Missouri’s corporate income tax nexus standard does not solely rely on physical presence or factor presence thresholds.

Federal law, Public Law 86-272, provides limited protection for out-of-state businesses. This law prohibits states from imposing a net income tax on income derived from within the state if the only business activity is the solicitation of orders for sales of tangible personal property. Orders must be sent outside the state for approval and filled from outside the state. If a corporation’s activities in Missouri extend beyond this protected solicitation, it may establish nexus and a filing requirement.

Exempt Entities

Certain types of entities are exempt from Missouri corporate income tax filing requirements. Non-profit organizations exempt from federal income tax under Internal Revenue Code Section 501(c)(3) are exempt from filing a Missouri corporate income tax return. This exemption applies unless they have unrelated business taxable income (UBTI) subject to federal income tax.

Missouri law provides statutory exemptions for other organizations. Express companies that pay an annual tax on their gross receipts in the state are exempt from corporate income tax. Insurance companies subject to an annual tax on their gross premium receipts in Missouri are also exempt. Certain Missouri mutual or extended Missouri mutual insurance companies organized under Chapter 380 of the Revised Statutes of Missouri also fall under these exemptions.

Required Forms and Information for Filing

Corporations subject to Missouri income tax must submit specific forms and financial information. The primary form for C-corporations is Form MO-1120, the Corporation Income Tax Return. S-corporations file Form MO-1120S, the S Corporation Tax Return, for informational purposes.

To complete these forms, a corporation needs federal taxable income, which is the starting point for Missouri’s tax calculation. Adjustments, such as Missouri additions and subtractions, are then applied to arrive at Missouri taxable income. If the corporation operates in multiple states, apportionment factors are necessary to determine the portion of income attributable to Missouri.

Details regarding applicable tax credits must also be compiled, as these can reduce a corporation’s tax liability. Supporting schedules from the federal return, such as Federal Form 1120 or 1120S and corresponding Schedule K-1(s) for S-corporations, must be attached to the Missouri return. Official forms and detailed instructions are available from the Missouri Department of Revenue’s website.

Submission Process and Deadlines

Once a Missouri corporate income tax return is prepared, corporations have several options for submission. Electronic filing is available for both Form MO-1120 and Form MO-1120S through the Modernized e-File (MeF) system. Paper returns can be submitted by mail to the Missouri Department of Revenue, ensuring the envelope is postmarked by the due date.

The standard filing deadline for Missouri corporate income tax returns is the 15th day of the fourth month following the close of the tax year. For calendar-year filers, this is April 15. If a federal extension to file (Form 7004) has been granted, Missouri automatically grants a corresponding six-month extension for the state return. A copy of the federal extension must be attached to the MO-1120 when filed.

An extension of time to file does not extend the time for payment of any tax due. Payment of estimated taxes or the final tax liability can be made electronically via e-check or credit card through the Missouri Department of Revenue’s online portal, or by mailing a check or money order. After submission, corporations should retain records; electronic filers receive an acknowledgment.