Before you start

An SSN or ITIN
Form W-4 with your employer for federal withholding
Missouri Form MO W-4 or Kansas Form K-4 with your employer, for the state you actually live in
Your work location and your home location, which in this metro are frequently in different states
Your county assessor, for the annual personal property declaration on the Missouri side

Step-by-step

1
Complete the federal W-4 and the correct state form on day one
Missouri's MO W-4 and Kansas's K-4 are not interchangeable. Give payroll the one for the state you live in, and tell them explicitly if your workplace is in the other state — that is what triggers the non-resident withholding and the credit arrangement.
Via employerWho: YouFirst week of employment
2
Work out whether the Kansas City earnings tax applies to you
It applies if you live inside the Kansas City, Missouri city limits, or if you work inside them — including if you live in Kansas and commute in. Note that the city limits are large and cross four Missouri counties, so 'in Kansas City' is a real boundary question rather than a vibe. Check the address before assuming.
OnlineWho: YouBefore your first payslip
3
If you are a non-resident who works some days elsewhere, file for the refund
Form RD-109NR lets a non-resident reclaim the earnings tax on whole days worked outside the city limits. For a hybrid or fully remote worker whose employer is downtown, this is a meaningful annual refund that is entirely opt-in — the city does not send it to you.
OnlineWho: YouWith the annual return
4
If you cross the state line to work, file two state returns
You file a non-resident return in the state you work in and a resident return in the state you live in, with the resident state giving a credit for tax paid to the other. Since a 2015 US Supreme Court decision, Kansas also allows a credit for the Kansas City, Missouri earnings tax on the K-40 — claim it, because it will not be applied for you.
OnlineWho: YouBy 15 April annually
5
Declare your personal property to the Missouri county assessor by 1 March
Missouri taxes vehicles, boats and trailers owned on 1 January, declared to your county assessor by 1 March and billed in the autumn. The paid receipt is what lets you renew your vehicle registration, so missing it costs twice.
OnlineWho: YouBy 1 March annually
6
Determine your US tax residency
The substantial presence test counts weighted days across three years to decide whether the US taxes your worldwide income or only US-source income. Your visa category does not decide this.
OnlineWho: You
7
Check for an applicable tax treaty
The US has treaties with around 70 countries that can reduce or exempt tax on particular income. Both Missouri and Kansas start from federal figures, so a federal treaty position generally flows through to the state return. The Kansas City earnings tax follows its own rules — confirm rather than assuming the treatment carries all the way down.
OnlineWho: You
8
File an FBAR if foreign accounts exceed $10,000
Aggregate foreign account balances over $10,000 at any point in the year trigger a FinCEN filing, separate from your tax return and with its own penalties.
OnlineWho: You

Documents you’ll need

Form W-2 from each employer, issued by 31 January — check the state and local boxes carefully
Form 1099s for freelance, interest and investment income
Forms W-4 and the correct state withholding form for where you live
Kansas City Form RD-109, or RD-109NR if you are a non-resident claiming days worked elsewhere
Missouri personal property declaration and paid tax receipt
Passport and travel history for the substantial presence day count
Foreign account statements for FBAR reporting

Things most newcomers don’t know

The earnings tax follows the workplace, and a remote worker can claim part of it back.

Form RD-109NR lets a non-resident reclaim the 1% on whole days physically worked outside the Kansas City, Missouri city limits. Since the pandemic reshaped where people work, that is a real annual refund for a lot of people who have never heard of the form. Roughly 46% of the tax is paid by non-residents, so this affects a very large share of the metro's workforce.

Source: City of Kansas City, Missouri — earnings tax

Kansas residents can credit the Kansas City earnings tax — but only if they claim it.

Kansas historically refused a credit for another state's local taxes. After a 2015 US Supreme Court decision on double taxation, the Kansas Department of Revenue changed its reading of the credit statute to include the Kansas City, Missouri earnings tax. It is not automatic and software does not always catch it; it is worth checking a return that was prepared without it.

Source: Kansas Department of Revenue

Both states tax your car every year, and Missouri makes it a condition of registration.

Missouri assesses personal property as of 1 January, declared by 1 March and billed in the autumn — and you cannot renew a vehicle registration without the paid receipt. Kansas collects its vehicle tax with the tag. For anyone arriving from a country with no annual vehicle tax this is an unbudgeted recurring cost and, on the Missouri side, a procedural gate.

Source: Jackson County Assessment / Missouri Department of Revenue

Kansas's low-sounding rate is not as low as it looks.

Kansas's 5.20%/5.58% brackets sit above Missouri's 4.7% top rate, and Kansas's standard deduction is far below the federal one, so more of your income is taxable. Comparing the two states on headline rate alone understates the gap. Run your actual salary through both before deciding which side to live on.

Source: Kansas Department of Revenue / Missouri Department of Revenue

Your visa does not determine your tax residency.

The substantial presence test — a weighted day count across three years — decides whether the US taxes your worldwide income. Someone on a temporary visa can be a US tax resident; someone on a long visa can fail the test. Do the count rather than assuming.

Source: IRS — substantial presence test

Common mistakes to avoid

Comparing Missouri and Kansas on headline income tax rate without accounting for Kansas's much smaller standard deduction.
Never filing Form RD-109NR when you work outside the city limits some days, and leaving the refund on the table.
Not claiming the Kansas K-40 credit for the Kansas City earnings tax.
Assuming a 'Kansas City' address is inside the city limits. They cross four counties and the boundary is irregular.
Missing the 1 March Missouri personal property declaration and then failing the registration renewal.
Missing the FBAR because a home-country account did not feel 'foreign'.

Some of this may be out of date. Spotted something inaccurate? Help us keep it right for the next newcomer.

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