A Kansas partnership return is filed on Form K-120S, the Kansas Partnership or S Corporation Income Tax Return, and is due one month after the federal Form 1065 deadline — April 15 for calendar-year partnerships. The partnership itself generally owes no Kansas income tax, but the return reports each partner’s distributive share so partners can pay tax on their individual returns. Since 2022, partnerships can also elect to pay tax at the entity level under the SALT Parity Act.
What You File and What Goes With It
Every partnership doing business in Kansas or earning income from Kansas sources must file Form K-120S and check the box indicating it is filing as a partnership rather than an S corporation.1Kansas Department of Revenue. Partnership or S Corporation Income Tax – 2025
Three things travel with the return:
- Pages 1 through 4 of the federal Form 1065 as filed with the IRS, plus any federal schedules that support Kansas modifications on page 1 of the K-120S. Missing the federal attachment is one of the most common filing errors and often triggers processing delays or follow-up notices.
- A distribution schedule showing each partner’s share of federal ordinary income, Kansas-source income, and Kansas modifications. Each partner uses those figures on their individual Kansas return (Form K-40).2Kansas Department of Revenue. 2005 Kansas Partnership or S Corporation Tax Booklet
- Any payment owed, submitted with Form K-120V, the corporate payment voucher.
Deadlines and Extensions
The K-120S is due one month after the federal partnership return. For calendar-year partnerships, that is April 15. Fiscal-year partnerships file by the 15th day of the fourth month after the end of their tax year. When a due date falls on a weekend or legal holiday, it moves to the next business day.1Kansas Department of Revenue. Partnership or S Corporation Income Tax – 2025
Kansas does not issue its own extension form. If you file federal Form 7004 with the IRS, enclose a copy with the completed K-120S and Kansas automatically grants a six-month extension, moving a calendar-year deadline to October 15. The extension buys time to file, not time to pay. Interest starts running on any unpaid balance from the original due date, and any payment owed with the extension goes on Form K-120V.
Who Actually Owes the Tax
Under K.S.A. 79-32,129, the partnership itself is not subject to Kansas income tax. Each partner reports their distributive share of partnership income on their own return and pays tax individually.3Justia. Kansas Code 79-32129 – Partners, Not Partnership, Subject to Tax One exception applies: a partnership that elects federally to be taxed as a corporation files and pays tax under Kansas’s corporate provisions, and its owners are treated as shareholders.
The SALT Parity Act Election
Since 2022, Kansas partnerships can make an annual election to pay income tax at the entity level under the SALT Parity Act (K.S.A. 79-32,286). The election exists as a workaround to the federal $10,000 cap on state and local tax deductions. When the partnership pays the tax, the deduction sits on the partnership return rather than the individual partner’s return, effectively bypassing the cap.
You make the election by checking Box N on the K-120S for the year in question. Only income attributable to individual owners qualifies; shares held by partners that are themselves partnerships or corporations cannot be included.4Kansas Department of Revenue. Frequently Asked Questions About the SALT Parity Act
The PTE tax rate equals the highest individual income tax rate for that year. For tax year 2024 and beyond, that rate is 5.58% under K.S.A. 79-32,110.5Kansas Office of Revisor of Statutes. Kansas Code 79-32110 – Tax Imposed; Classes of Taxpayers; Schedules of Tax Rates Each electing partner then claims a credit on their individual Kansas return for their share of the entity-level tax paid, which avoids double taxation.4Kansas Department of Revenue. Frequently Asked Questions About the SALT Parity Act
Estimated Payments
A partnership that elects the PTE tax or otherwise expects a Kansas tax liability over $500 must make quarterly estimated payments on Form K-120ES. Payments are due on the 15th of the 4th, 6th, 9th, and 12th months of the partnership’s tax year. For a calendar-year filer, that means April 15, June 15, September 15, and December 15.6Kansas Department of Revenue. 2026 Kansas Corporate Estimated Tax Voucher for K-120 and K-120S Underpayment triggers a separate penalty calculated on Schedule K-220S.
Multi-State Partnerships and Apportionment
A partnership earning income both inside and outside Kansas does not pay Kansas tax on all of it. Kansas apportions income using a three-factor formula that averages the partnership’s property, payroll, and sales within Kansas as a proportion of its property, payroll, and sales everywhere.7Legal Information Institute. Kansas Admin Regs 92-12-83 – Apportionment Formula
A qualifying partnership may elect a two-factor formula that uses only property and sales, dropping payroll. Which method produces the better result depends on where employees and assets sit relative to the customer base. Two apportionment errors show up repeatedly: misclassifying business income as non-business income (which gets allocated to a single state instead of apportioned), and incorrectly sourcing sales, especially service revenue.
Non-Resident Partners
Kansas repealed mandatory withholding on non-resident partners’ distributive shares in 2014, so the partnership no longer needs to withhold Kansas tax for a non-resident partner.8Kansas Department of Revenue. Withholding Repealed for Nonresident Shareholders of S Corporations, Partners, and Members of Limited Liability Companies Non-resident partners still owe Kansas tax on their Kansas-source income and must file individually.
To simplify that, a partnership can file a composite return, Schedule K-40C, on behalf of its non-resident partners. A partner qualifies for inclusion only if they have no Kansas-source income outside the partnership. No advance approval from the Department of Revenue is required, but a composite return cannot be filed if the partnership is claiming a special tax credit or a net operating loss for the year, and partners included in a composite return cannot also file their own separate Kansas return.9Kansas Department of Revenue. K-40C Composite Income Tax Schedule Instructions
Amended Returns After a Federal Change
If the IRS adjusts your partnership’s federal return through audit or other change, Kansas requires an amended K-120S within 180 days of the date the federal adjustments are paid, agreed to, or become final, whichever comes first. Include a copy of the Revenue Agent’s Report or adjustment letter showing and explaining the changes.10Kansas Office of Revisor of Statutes. Kansas Code 79-3230 – Tax Information, Report and Returns Missing the 180-day window exposes the partnership to the same penalties that apply to a late original filing.
If the amendment produces a refund, it must be filed within three years from the original due date (including extensions) or two years from when the overpaid tax was actually paid, whichever is later.
Penalties and Interest
Kansas imposes escalating penalties under K.S.A. 79-3228 based on the violation:
- Late filing or late payment: for tax years ending after December 31, 2001, the penalty is 1% of the unpaid tax for each month or fraction of a month the return or payment is late.11Kansas Office of Revisor of Statutes. Kansas Code 79-3228 – Penalties and Interest
- Post-audit assessment: if a field audit shows additional tax owed on a return that was filed and paid, the penalty is 10% of the unpaid balance in the assessment notice.
- Failure to make a reasonable attempt to comply: 25% of the unpaid balance if the Department finds a serious lack of effort to follow the law.
- Fraud: 100% of the unpaid tax, effectively doubling the amount owed.
Interest also accrues on any unpaid tax from the original due date until paid in full. For 2026, the rate under K.S.A. 79-2968 is 8%.12Kansas Department of Revenue. Interest Rates for Calendar Year 2026 Penalty and interest compound quickly, so a return that is both late and underpaid can grow well beyond the original tax bill.
Common Filing Mistakes
Errors on Kansas partnership returns tend to cluster in a few places. Apportionment tops the list for multi-state partnerships. The three-factor formula reads as simple, but classifying income as business or non-business and sourcing service sales correctly trips up experienced preparers.
Partner allocation errors on the distribution schedule create cascading problems. When allocations do not match the partnership agreement, or when special allocations lack substantial economic effect, every affected partner’s individual Kansas return is wrong. This shows up most in partnerships where profit-sharing ratios differ from ownership percentages.
Finally, some filers still reference Form K-65 or look for a Kansas-specific extension form. Kansas merged the old partnership-specific Form K-65 into the K-120S starting with the 2005 tax year, and there is no Kansas extension form: extensions require a copy of federal Form 7004 enclosed with the completed K-120S.1Kansas Department of Revenue. Partnership or S Corporation Income Tax – 2025
Record Retention
Kansas law requires that all tax reports and returns be preserved for at least three years, and thereafter until the director of taxation orders them destroyed.13Kansas State Legislature. Kansas Code 79-3234 – Tax Information, Report and Returns; Preservation Because Kansas allows amended returns for up to three years from the original due date and the IRS can audit federal returns for up to three years (or six years when substantial income is omitted), keeping records at least six years is prudent. Records supporting the apportionment calculation, partner allocation agreements, and any PTE election deserve particular care.
A Separate Filing: The Biennial Information Report
The Kansas partnership return covers tax. It does not cover the entity’s registration with the Secretary of State. Partnerships registered in Kansas must also file an Information Report every two years. For-profit partnerships file by April 15 of their designated odd or even year, based on when the business was formed, and there is a three-month grace period after the due date.14Kansas Secretary of State. Information Reports Missing the grace period puts the business into forfeited status, which strips its authority to transact business in Kansas until it files the overdue reports and a reinstatement form.15Business Center One Stop. Maintaining Good Standing Status