MO-MSS: S Corporation Allocation and Apportionment Form and Instructions (2025)
Missouri · Missouri DOR · Used for tax years 2025
Form MO-MSS is Missouri’s 2025 S-Corporation Allocation and Apportionment Schedule, attached to Form MO-1120S. It reports the method and percentage used to apportion income to Missouri, along with any directly allocated nonapportionable income and related expenses.
Who files this form
Use the 2025 Form MO-MSS to allocate and apportion an S corporation’s income using the Receipts Factor Apportionment Method or another appropriate method. Attach it to Form MO-1120S.
A taxpayer must have income from more than one state to allocate and apportion income. Do not complete this form if all income is from Missouri sources.
Corporations that qualify as broadcasters under 12 CSR 10-2.260 must choose Method Seven.
What you'll need
Have the following information and forms available:
- Corporation name, Missouri tax ID number, charter number, federal employer ID number, and taxable-year beginning and ending dates.
- Form MO-1120S, which the MO-MSS must be attached to, and Form MO-NRS, where the calculated percentages are entered.
- Missouri receipts and total receipts everywhere for Method Two A.
- Missouri miles and total miles for Methods Three through Six, if applicable.
- Gross income and related expenses, both everywhere and in Missouri, for any nonapportionable income being allocated.
- Partnership factors and the corporation’s ownership percentage, if the corporation owns an interest in a partnership.
Required attachments depend on your situation:
- An explanation and computations supporting nonapportionable income, plus a similar table for distributive share items not listed on the form.
- A detailed explanation for special Methods Three through Seven.
- For Method Seven, either a prior approval letter or an explanation identifying the authorizing Missouri regulation and why the corporation qualifies.
- A detailed statement explaining any reasonable approximation used when the states to which receipts should be assigned cannot be determined.
How to file
- Enter the corporation’s identifying information and taxable-year dates.
- Select only one apportionment method.
- For Method Two A, enter Missouri receipts on Part 1, Line 1 and total receipts everywhere on Line 2. Divide Line 1 by Line 2 to calculate the receipts factor on Line 3.
- Complete the applicable nonapportionable-income entries and supporting calculations. Follow the special-method instructions if using Methods Three through Seven.
- Enter the applicable percentages on Form MO-NRS, Parts 1 and 2, Column (c). An item with nonapportionable income may require a separately calculated percentage.
- Attach Form MO-MSS and required explanations to Form MO-1120S and mail to the Missouri Department of Revenue.
The form prints this address for refund or no amount due returns:
Missouri Department of Revenue
P.O. Box 336
Jefferson City, MO 65105-0336
Common mistakes
- Completing MO-MSS when all income is from Missouri sources. The form says not to do this.
- Selecting more than one apportionment method. Select only one box.
- Treating income as nonapportionable without support. All income is presumed apportionable unless you can clearly show otherwise.
- Allocating expenses that were excluded from federal taxable income. The form expressly prohibits this.
- Including receipts from hedging transactions or dispositions of cash or securities in the receipts factor. These receipts must be excluded from both the Missouri and everywhere totals.
- Using Method Seven without prior approval or an authorizing industry-specific Missouri regulation, or omitting the required supporting attachment.
Questions people ask
How is the receipts factor calculated?
Divide Missouri receipts on Part 1, Line 1 by total receipts everywhere on Line 2. Enter the resulting percentage on Line 3 and transfer it to Form MO-NRS as directed.
Are interest, dividends, rents, and royalties automatically nonapportionable income?
No. The instructions say these labels do not determine whether income is apportionable or nonapportionable. All income is presumed apportionable unless you can clearly show it is nonapportionable.
What if the corporation owns part of a partnership?
Multiply the partnership’s factors by the corporation’s ownership percentage, then add the results to the corporation’s apportionment factors.
What if a nonapportionable distributive share item is not listed on the form?
Attach a table similar to the one on the form for that item. Also attach an explanation and computations detailing the nature of the nonapportionable income.