What actually happens
An employee who lives in Kansas and performs work in Missouri sits in two tax systems at once. The residence state claims the right to tax all of a resident's income wherever earned; the work state claims the right to tax income sourced within its borders. Absent an agreement, both claims stand, and the conflict is resolved after the fact through a credit on the resident return rather than up front in payroll.
When Missouri withholding starts
Missouri requires withholding from the first dollar of in-state compensation. There is no de minimis day count to shelter a short assignment. No day-count safe harbor for withholding; withhold on Missouri-source wages. Tax Foundation reports a $600 Missouri-source income nonresident FILING threshold, which is a return-filing rule rather than a withholding safe harbor.
The trap is that thresholds are usually retroactive to the first day once crossed. An employee who spends 40 days in a 30-day-threshold state does not owe tax on 10 days; they owe it on all 40, and the employer is the one who failed to withhold.
Unemployment insurance goes to one state only
Income tax can be split between states. Unemployment insurance cannot. Under the localization test used by every state, an employee whose services are performed entirely in Missouri is covered by Missouri for unemployment purposes, and all wages are reported there — regardless of where they live, where you are headquartered, or which state's income tax you withhold. Missouri's 2026 taxable wage base is $9,000. The four-factor test in order.
Local taxes are a separate problem
Missouri: Kansas City and St. Louis each impose a 1% earnings tax on residents and on nonresidents for work performed in the city, withheld by employers. Both cities also impose employer-side payroll expense taxes.
Kansas: Some Kansas counties and townships levy a local intangibles tax on interest and dividend income only. It does NOT apply to wages and is NOT withheld through payroll -- for payroll purposes Kansas should be treated as having no local wage tax.
What you have to register for
| Obligation | State | Agency |
|---|---|---|
| Income tax withholding | Missouri | Missouri Department of Revenue |
| Unemployment insurance | Missouri | Missouri Department of Labor, Division of Employment Security |
Frequently asked
Do Missouri and Kansas have a reciprocal tax agreement?
No. There is no reciprocal agreement between Missouri and Kansas. Missouri taxes wages earned in the state by nonresidents, and Kansas taxes the same wages as resident income while allowing a credit for tax paid to Missouri.
Which state's income tax should be withheld?
Missouri, as the state where the work is performed. Kansas also taxes the income as a resident, but the employee claims a credit on the Kansas return for tax paid to Missouri.
Which state gets the unemployment insurance wages?
Missouri. Unemployment coverage is never split between states for a single job. The localization test assigns the whole job to the state where services are performed, which here is Missouri, regardless of residence or where the employer is headquartered.
How many days can an employee work in Missouri before withholding starts?
There is no safe harbour. Missouri requires nonresident withholding from the first dollar of compensation earned in the state, so even a single day of in-state work creates an obligation in principle.