Missouri Form MO-A is the adjustments schedule that turns your federal adjusted gross income into your Missouri AGI on the MO-1040. You need it if you earned interest from out-of-state bonds, receive a pension or Social Security, have military pay, hold U.S. Treasury interest, or itemize deductions. If none of those apply and you take the standard deduction, you can file the MO-1040 without it. The form has three parts, and you complete only the ones that fit your situation.
When You Can Skip Form MO-A
Missouri Revised Statutes Section 143.121 lists the specific additions and subtractions that convert federal AGI into Missouri AGI.1Missouri Revisor of Statutes. Missouri Code 143.121 – Missouri Adjusted Gross Income If none of these apply to you and you take the standard deduction, you don’t need Form MO-A at all. The most common triggers are:
- Interest from bonds issued by other states or their local governments (federally tax-exempt, taxable in Missouri)
- Interest from U.S. Treasury obligations (federally taxable, exempt in Missouri)
- A pension, annuity, IRA, or 401(k) distribution
- Social Security or Social Security disability benefits
- Active-duty, reserve, or National Guard military pay, or military retirement
- A prior-year Missouri refund that appeared as income on your federal return
- Itemized deductions on your federal Schedule A
What to Gather Before You Start
Most MO-A lines reference specific federal line numbers, so keep your completed federal return in front of you. Pull together:
- Your Federal Form 1040 and any Schedules A, B, C, E, or F you filed
- 1099-INT and 1099-DIV forms with issuer-level detail so you can separate Missouri interest from other-state interest and identify U.S. government interest
- SSA-1099 for Social Security benefits
- 1099-R forms for each pension, annuity, IRA, or 401(k) distribution, with a note on whether the source is a government (public) plan or a private plan, because Missouri calculates their exemptions separately
- W-2s or pay statements for active-duty, reserve, or National Guard service
- Federal Schedule A, including the state and local tax breakdown on Line 5a, if you itemize
Part 1: Additions and Subtractions
Part 1 is where most filers spend their time. Additions on Lines 1 through 7 increase your Missouri AGI above the federal figure; subtractions on Lines 8 through 19 decrease it.2Missouri Department of Revenue. Form MO-A 2025 Individual Income Tax Adjustments
Additions
The most common addition is out-of-state municipal bond interest on Line 1. If you own a diversified bond fund, check the year-end tax statement, which breaks interest down by state. Only the non-Missouri portion belongs on this line.1Missouri Revisor of Statutes. Missouri Code 143.121 – Missouri Adjusted Gross Income
Other additions cover net operating loss carrybacks or carryforwards from partnerships, fiduciaries, or S corporations (Line 2), nonqualified distributions from 529 education savings plans (Line 3), food pantry contributions already claimed on federal Schedule A (Line 4), property taxes paid to another state by nonresidents (Line 5), and nonqualified ABLE account distributions (Line 6). Line 7 totals the six.
Subtractions
Subtractions are where Missouri returns money to most filers. The biggest ones:
- U.S. government obligation interest on Line 8. Treasury bills, bonds, notes, and savings bond interest come off Missouri income. Attach a detailed list or the 1099 forms that show these amounts.
- Prior-year Missouri state refund on Line 9, if it appeared as income on your federal return.
- Military retirement benefits on Line 10, which Missouri fully exempts.
- Contributions to Missouri’s 529 education savings plan on Line 12, up to certain limits.
- Business income deduction on Line 17 for self-employed filers and pass-through entity owners. The percentage is capped at 20% and phases in based on state revenue triggers; use the worksheet in the MO-1040 instructions to figure your amount.3Missouri Revisor of Statutes. Missouri Code 143.022 – Business Income Deduction
- Capital gain deduction on Line 18 for a portion of certain capital gains.
Line 19 totals all subtractions. Line 7 minus Line 19 gives you the Part 1 net modification, which carries to your MO-1040.
Part 2: Missouri Itemized Deductions
Complete Part 2 only if you itemized on your federal return. If you took the standard deduction, skip it.
Part 2 starts with your total federal itemized deductions from Form 1040, Line 12e, and makes two adjustments.2Missouri Department of Revenue. Form MO-A 2025 Individual Income Tax Adjustments On Lines 2 through 7, you add back payroll taxes that are not deductible federally: Social Security tax, Railroad Retirement tax (Tier I and Tier II), Medicare tax, and self-employment tax. Then you subtract the state and local income taxes you claimed on federal Schedule A, Line 5a, minus any local earnings taxes. Missouri doesn’t let you deduct state income tax from state income.
Line 12 gives your Missouri itemized deduction. Compare it to the Missouri standard deduction for your filing status before you commit. If the standard deduction is higher, you can take it on your MO-1040 even though you itemized federally; Missouri lets you make a different choice on this point.
Part 3: Pensions and Social Security
Part 3 has four sections, and the rules changed starting with tax year 2024, when Missouri removed the income-based limits that previously capped these deductions.4Missouri Department of Revenue. Pension Tax Year 2024 FAQs
Section A: Public Pension
If you receive a pension from a federal, state, or local government source (military retirement, MOSERS, PSRS, a federal civil service annuity, and similar plans), you can subtract those benefits up to the maximum Social Security benefit amount for the year, provided they are included in your federal AGI.5Missouri Department of Revenue. Pension FAQs If you also claim the Social Security deduction, your public pension exemption is reduced by that amount.
Section B: Private Pension
Distributions from 401(k) plans, IRAs, private-company pensions, and annuities have their own calculation in Section B, with a separate worksheet and a smaller exemption than Section A.
Section C: Social Security and Social Security Disability
For tax years 2024 and later, Missouri exempts 100% of Social Security benefits for taxpayers who are age 62 or older by December 31 of the tax year. Social Security disability benefits are fully exempt regardless of age. The benefits must be included in your federal AGI under IRC Section 86 to qualify for the Missouri subtraction.5Missouri Department of Revenue. Pension FAQs Check the “62 and older” box on page 1 of your MO-1040 if you’re claiming the age-based exemption.
Section D: Total
Section D combines the results from Sections A, B, and C into a single pension and Social Security subtraction that feeds back into your MO-1040.
Military Income Deduction
Under Section 143.174, 100% of active-duty military pay earned as a member of the Armed Forces can be subtracted from Missouri AGI, including signing bonuses.6Missouri Revisor of Statutes. Missouri Code 143.174 – Active Duty Military Income Deduction On a combined return, the deduction applies to the military portion of your combined AGI.
Reserve and National Guard members get a separate deduction under Section 143.175. Beginning in tax year 2024, inactive-duty income from National Guard training and Armed Forces Reserve components is 100% deductible as well.7Missouri Department of Revenue. Military Income Deduction Information Both deductions come off in Part 1 of Form MO-A. Military retirement benefits go on Line 10 separately.8Missouri Department of Revenue. Military Information
Filing Form MO-A With Your Return
Form MO-A is never filed on its own. It goes in with your MO-1040, whether you file electronically or on paper, and it’s due April 15, 2026, for the 2025 tax year. Most commercial tax software handles Form MO-A automatically as part of the state return, and the Department of Revenue lists approved free e-file providers on its website.9Missouri Department of Revenue. Online Filing of Federal and State Income Tax Returns
If you file by mail, clip or staple Form MO-A behind your MO-1040. The address depends on whether you owe:10Missouri Department of Revenue. Missouri Department of Revenue Now Accepting E-filed State Tax Returns
- Balance due: Missouri Department of Revenue, P.O. Box 329, Jefferson City, MO 65105-0329
- Refund or zero balance: Missouri Department of Revenue, P.O. Box 500, Jefferson City, MO 65105-0500
If You Make a Mistake
Missing the April deadline or underpaying triggers automatic penalties. Missouri charges 5% per month for failure to file, up to 25% of the unpaid balance, and a separate 5% penalty for failure to pay by the due date, with interest on top.11Missouri Department of Revenue. Individual Income Tax FAQs
If you spot an error on Form MO-A after filing, correct it by filing an amended MO-1040 for that tax year with the amended return box checked, and attach a corrected Form MO-A.12Missouri Department of Revenue. How Do I Correct a Filing Mistake If the IRS adjusts your federal return, Missouri expects an amended state return reflecting those changes. The two agencies share taxpayer data, and discrepancies tend to surface.