How to File Missouri Form MO-1120S: Deadlines, PTE, and Nonresidents

To file Missouri Form MO-1120S, complete the S-Corporation income tax return using figures from your federal Form 1120-S, make the Missouri-specific adjustments on Page 3, attach the required federal forms and any nonresident shareholder schedules, and submit it to the Missouri Department of Revenue by the 15th day of the fourth month after your tax year ends.1Missouri Department of Revenue. Missouri Form MO-1120S S-Corporation Income Tax Return Instructions2Cornell Law Institute. 12 CSR 10-2.190 – Partnership and S Corporation Annual Return Filing Requirements, Composite Returns, and Nonresident Partner/Shareholder Income Tax Withholding For most S-Corporations, the return is informational: the entity owes no Missouri income tax, and each shareholder reports their share of income on an individual return.3Missouri Department of Revenue. Corporation Income Tax

Who Has to File

If your corporation filed a federal Form 1120-S, you also owe Missouri a MO-1120S whenever at least one shareholder is a Missouri resident or the corporation has any Missouri-source income.1Missouri Department of Revenue. Missouri Form MO-1120S S-Corporation Income Tax Return Instructions File even in a loss year. The duty comes from 12 CSR 10-2.190, which ties the state return directly to the federal S election.2Cornell Law Institute. 12 CSR 10-2.190 – Partnership and S Corporation Annual Return Filing Requirements, Composite Returns, and Nonresident Partner/Shareholder Income Tax Withholding

What to Gather Before You Start

  • Your completed federal Form 1120-S and every Schedule K-1. Copies of both attach to the Missouri return.1Missouri Department of Revenue. Missouri Form MO-1120S S-Corporation Income Tax Return Instructions
  • Your Federal Employer Identification Number (FEIN) and Missouri Tax Identification Number. If the corporation is not yet registered with the Department of Revenue, register online at dor.mo.gov, by calling Business Registration at (573) 751-5860, or by mail to the Taxation Division at P.O. Box 3300, Jefferson City, MO 65105-3300.4Missouri Department of Revenue. Missouri Form MO-1120S S-Corporation Income Tax Return
  • Any federal Form 8886 reportable transaction disclosures you filed with the IRS.1Missouri Department of Revenue. Missouri Form MO-1120S S-Corporation Income Tax Return Instructions
  • Form MO-MSS if the corporation earned income in more than one state.
  • Forms MO-NRS, MO-1NR, and MO-2NR if any shareholder is a nonresident individual.

Completing the Return

The header takes the corporation’s name, address, FEIN, and Missouri Tax ID. From there, the return pulls numbers from your federal 1120-S (ordinary business income, rental income, interest, dividends, other pass-through items) and then asks you to reconcile them to Missouri rules.

Missouri Adjustments

Page 3 is where federal and state treatment part ways. Interest income from other states’ bonds is the most common example: the federal return excludes it, but Missouri taxes it. Each adjustment line has columns that break out the total S-Corporation amount and each shareholder’s share.1Missouri Department of Revenue. Missouri Form MO-1120S S-Corporation Income Tax Return Instructions Errors here tend to generate corrected assessments and knock-on delays for the shareholders’ individual returns, so work through them carefully.

Multistate Apportionment

If the corporation earns income outside Missouri, do not report all of it as Missouri-source. Complete Form MO-MSS to allocate and apportion using the Receipts Factor Apportionment Method or another approved method. The Missouri apportionment percentage from MO-MSS, Line 3 carries to Form MO-NRS (Part 1, Line 1, Column c) and sets how much of each shareholder’s income Missouri taxes.1Missouri Department of Revenue. Missouri Form MO-1120S S-Corporation Income Tax Return Instructions When a particular item is wholly or partially nonapportionable, compute a separate percentage for it and attach a written explanation.

Nonresident Shareholder Schedules

If every shareholder is a Missouri resident, skip this section. Otherwise, two sets of paperwork come into play.

Form MO-NRS

Prepare a separate MO-NRS for each nonresident shareholder when the corporation has Missouri-source income. Each form needs the shareholder’s name and Social Security Number from the federal K-1, the corporation’s FEIN, and the Missouri apportionment percentage from MO-MSS. Part 1 multiplies federal Schedule K amounts by that percentage to get Missouri-source figures; Part 2 carries amounts from the MO-1120S adjustment lines and splits out each nonresident’s share. Attach the completed MO-NRS forms to the MO-1120S.5Missouri Department of Revenue. MO-NRS S Corporation Nonresident Form

Withholding: Forms MO-1NR and MO-2NR

Missouri requires the S-Corporation to withhold on behalf of nonresident individual shareholders unless an exemption applies. The rate is 4.7 percent of the shareholder’s Missouri-source income.6Missouri Department of Revenue. Form MO-2NR Statement of Income Tax Payments For Nonresident Individual Partners or S Corporation Shareholders File Form MO-1NR to report the total withheld, and issue Form MO-2NR to each shareholder subject to withholding, even if no tax was actually withheld or the shareholder has an exemption on file.1Missouri Department of Revenue. Missouri Form MO-1120S S-Corporation Income Tax Return Instructions Three limits worth knowing:

How and Where to File

Electronic Filing

S-Corporations can file through the IRS Modernized E-File (MeF) system. You can send the federal and Missouri returns together through an IRS-approved Electronic Return Originator (ERO), or transmit the MO-1120S as a stand-alone state return through an ERO.4Missouri Department of Revenue. Missouri Form MO-1120S S-Corporation Income Tax Return A list of approved vendors that support corporate e-filing is maintained at dor.mo.gov.

Paper Filing

Mail the signed return with every required attachment to:

Missouri Department of Revenue
P.O. Box 336
Jefferson City, MO 65105-03367Missouri Department of Revenue. MO-1120S S-Corporation Income Tax Return

Paper returns take several weeks to process. Electronic filing gives near-immediate confirmation and avoids transcription errors.

Deadline and Extensions

The MO-1120S is due by the 15th day of the fourth month after the close of the tax year.2Cornell Law Institute. 12 CSR 10-2.190 – Partnership and S Corporation Annual Return Filing Requirements, Composite Returns, and Nonresident Partner/Shareholder Income Tax Withholding Calendar-year filers file by April 15. When the date lands on a weekend or holiday, it moves to the next business day.

If you obtained a federal extension by filing Form 7004, Missouri automatically gives you the same extension period. Check the extension box at the top of the MO-1120S and attach a copy of the approved federal Form 7004.1Missouri Department of Revenue. Missouri Form MO-1120S S-Corporation Income Tax Return Instructions File a separate Missouri Form MO-60 only when you expect to owe tax and need to submit a payment with the extension. If you owe nothing, the federal extension stands on its own. An extension to file is not an extension to pay. Unpaid tax after the original deadline draws a penalty of 5 percent per month, up to 25 percent total, plus interest.8Missouri Department of Revenue. Form MO-60 – 2025 Application For Extension of Time to File

Two Elections to Decide Before You File

Pass-Through Entity Tax (Form MO-PTE)

Missouri’s SALT Parity Act, codified at Section 143.436 RSMo, lets an S-Corporation elect to pay Missouri income tax at the entity level rather than passing the full liability through to shareholders.9Missouri Revisor of Statutes. Missouri Code 143.436 – SALT Parity Act10Cornell Law Institute. Missouri Code 12 CSR 10-2.436 – SALT Parity Act Implementation11Missouri Department of Revenue. 2025 Individual Income Tax Year Changes Electing entities are not required to make estimated payments of the PTE tax, so there is no underpayment penalty specific to the election, though an entity may pay early using Form MO-PTEAP.12Missouri Department of Revenue. FAQs – Pass-Through Entity Tax

Composite Return for Nonresidents

If the corporation has nonresident shareholders who otherwise would not need to file a Missouri individual return, you can file a composite return and pay their Missouri tax in a single filing. Composite returns go on Form MO-1040, not on a separate corporate form: check the composite box at the top, put the corporation’s FEIN in the Social Security Number field, and put the corporation name in the name field.13Missouri Department of Revenue. Instructions for Composite Individual Return for Nonresident Partners or Shareholders Shareholders included on a composite return are excluded from MO-1NR and MO-2NR withholding.6Missouri Department of Revenue. Form MO-2NR Statement of Income Tax Payments For Nonresident Individual Partners or S Corporation Shareholders

The PTE election and the composite return serve different purposes and can interact in ways that affect how credits and withholding flow to shareholders. If the ownership group mixes residents and nonresidents, settle both questions with a tax professional before you file, not after.