If you run your business as an LLC, an S corporation, a partnership, or a sole proprietorship, your state government may have just given you a raise — or your competitor's state did. Iowa taxed top-bracket income at nearly 9 percent not long ago; today it taxes every dollar at a flat 3.8 percent. Ohio moved to a flat 2.75 percent back in January. Mississippi is phasing its income tax down year by year with elimination in sight. And Iowa is not an outlier: eight states enacted laws moving from graduated to flat income taxes in just four years, after only four states had made that same move in the entire previous century.
This guide covers which states have gone flat, which are cutting without going flat, which are racing all the way to zero — and, most importantly, what each of those moves means for your marginal rate, your estimated payments, and your expansion plans.
Flat vs. Graduated: Why the Structure Matters as Much as the Rate
Under a graduated income tax, your rate climbs as your income climbs: the first dollars are taxed lightly and only your last dollars face the top rate. Under a flat tax, every dollar of taxable income faces the same single rate, whatever you earn.
The practical difference is bigger than it looks, and it is not really about filling out the return. Tax tables make graduated math easy enough. A flat rate matters for three reasons that hit owners directly:
You make decisions on the margin. Choices about hiring, expanding, taking on one more contract, or investing in equipment turn on what happens to the next dollar of income, not the average of all prior dollars. A single rate makes that calculation instant and transparent: every extra dollar of profit keeps the same share.
Flat rates are harder to raise. A graduated system invites targeted hikes — a new bracket here, a surcharge there — that land on a narrow slice of taxpayers while the majority shrugs. A flat rate is all-in by construction: raising it hits every taxpayer at once, which is politically far harder. That history bears out. Every state that moved from graduated to flat rates before 2023 has since cut its flat rate further, by roughly half a point to a point and a half. Taxpayers seem to sense this intuitively: when Illinois voters were offered a graduated tax in 2020 with lower rates promised for most people, they rejected it decisively rather than hand lawmakers a dial they could turn later.
Your business rate is the individual rate. About 95 percent of American businesses are pass-through entities — sole proprietorships, partnerships, LLCs, and S corporations — whose profits are taxed on their owners' individual returns, not at corporate rates. For the vast majority of small businesses, the state's top individual marginal rate is the business tax rate. A cut in that rate is a business tax cut, full stop.
The Eight States That Went Flat Since 2021
Between July 2021 and June 2025, eight states enacted laws transitioning from graduated to single-rate individual income taxes. Seven are already in effect; the eighth, Kansas, phases in as revenue triggers are met.
| State | Flat rate | Status |
|---|---|---|
| Arizona | 2.5 percent | In effect since January 2023 — the lowest flat rate in the nation |
| Iowa | 3.8 percent | In effect since January 2025, accelerated a year early and cut below the original 3.9 percent target |
| Louisiana | 3 percent | In effect since January 2025, replacing brackets of 1.85 to 4.25 percent, with a higher $12,500 standard deduction |
| Mississippi | 4.4 percent for 2025 | Phasing down: 4.0 percent in 2026, then 3.75, 3.5, and 3.25 percent through 2029, with triggers for further cuts |
| Georgia | 5.19 percent for 2025 | Dropping toward 4.99 percent as revenue triggers are met |
| Idaho | 5.3 percent for 2025 | Cut twice since the flat tax took effect in 2023 |
| Kansas | Targeting 4 percent | Enacted April 2025; the phase-in fires as revenue growth and rainy-day-fund triggers are met |
| Ohio | 2.75 percent | In effect since January 2026 on nonbusiness income over $26,050 — the second-lowest flat rate in the country |
These eight join the earlier flat-tax states: Colorado (flat since 1987), Utah (2007), North Carolina (2014), and Kentucky (2019), plus Illinois, Indiana, Michigan, and Pennsylvania, which have been flat for decades. That brings the national count to 14 single-rate states, against nine states with no individual income tax on wages at all and 27 states plus the District of Columbia still on graduated schedules. Massachusetts shows the direction can reverse: voters added a 4-point surtax on income over $1 million starting in 2023, dismantling that state's centuries-old flat tax.
Cutting Further — and Racing All the Way to Zero
The newly flat states get the headlines, but a second group of states is cutting aggressively inside graduated or already-flat systems. In effect for the 2026 tax year:
- North Carolina trims its flat rate from 4.25 to 3.99 percent.
- Kentucky cuts its flat rate from 4 to 3.5 percent.
- Indiana drops its flat rate to 2.95 percent.
- Oklahoma cuts its top rate from 4.75 to 4.5 percent while simplifying brackets.
- Nebraska cuts its top rate to 4.55 percent, with a path toward 3.99 percent.
- Montana cuts its top rate to 5.65 percent.
- South Carolina cuts its top rate from 6 to 5.21 percent.
- Arkansas joins the 2026 cutting cohort as well.
Then there is the race to zero. Mississippi's phasedown law aims to keep cutting past 3 percent toward full elimination as revenues allow, and Oklahoma enacted an elimination path of its own in 2025. If either state finishes the job, it would join the nine states that already go without an individual income tax.
Watch the nearly-flat graduated states, too. Alabama's top rate kicks in at just $3,000 of income, saving the typical filer about $40 versus taxing everything at the top rate — a graduated system in name only, created by decades without inflation indexing. Missouri and Oklahoma have top rates kicking in at or below $10,000. These are the likeliest next candidates to finish the job and go formally flat.
Why Owners Feel This More Than Employees
An employee in a cutting state gets a somewhat larger paycheck. An owner gets that plus a lower tax rate on every dollar of business profit — and a changed answer to every marginal decision the business faces.
Pass-through profit is personal income. If your S corporation nets $200,000, that profit flows to your individual return. In Iowa, the state tax on that profit fell from roughly five figures under the old graduated top rate to a flat 3.8 percent calculation. Multiply that across years and it is real expansion capital: a hire, a truck, a marketing budget.
Lower marginal rates change yes-or-no calls. A project with a thin pre-tax return can flip from reject to accept when the state takes 3 cents of the next dollar instead of 6. Over a portfolio of small decisions — overtime shifts, a second location, new equipment — the cumulative effect compounds.
Certainty has value beyond the rate itself. A flat rate that is structurally hard to raise lets you model five-year plans without guessing which bracket your growth will land in. Site selection, entity choice, and owner compensation (salary versus distributions in an S corporation) all get simpler inputs.
Mind the federal interplay. Since 2017, Congress has capped the federal deduction for state and local taxes, which blunts the federal benefit of high state taxes for itemizers; 2025 legislation raised that cap temporarily. Separately, most states now offer a pass-through entity tax election that lets the business pay state tax at the entity level instead of passing the whole liability to owners' personal returns. As state rates fall, the math on that election shifts — the federal workaround matters less when the underlying state bill shrinks — so re-run it rather than assuming last year's election is still optimal. Election deadlines are strict and many are early in the year.
Income tax is one slice of the burden. States cutting income taxes sometimes lean harder on property taxes, sales taxes, or gross-receipts taxes to balance the books. A 2-point income tax cut paired with a reassessment that doubles your commercial property bill may not be the win it appears. Always model the total burden — income, property, sales, unemployment insurance, fees — before deciding a state is cheap.
What to Do Before Year-End: A Five-Item Checklist
1. Re-run your estimated payments. A lower rate means a lower required annual payment, and continuing last year's quarterly estimates hands the state an interest-free loan until refund season. Worse, if you moved into a higher-tax situation (new nexus in a graduated state, for example), last year's pace can leave you underpaid and penalized. Recompute federal and state estimates on current-year law now, while there is still a January payment to true up.
2. Revisit your pass-through entity tax election. If your state offers one, confirm the election deadline, the payment schedule, and whether the reduced individual rate changes the benefit. Some elections are binding once made; some require annual renewal. Put the deadline on the calendar with a two-week lead — this is the single most commonly missed state-tax election in small business.
3. Model total burden before applauding (or relocating). Build a simple comparison: state income tax on your actual profit, plus property tax on business real estate and equipment, plus sales tax you absorb on inputs, plus unemployment and workers' compensation differentials. States publish the inputs; your bookkeeper can assemble the comparison in an afternoon. Relocation decisions made on the income-tax headline alone are how owners discover the property-tax surprise a year later.
4. If you are considering a move, learn nexus before you lease. Moving your domicile does not move income your old state can still tax. States tax business income sourced within their borders through apportionment formulas — rules that slice your multi-state profit among the states where you operate — and remote employees, inventory, or even regular customer visits can create filing obligations, known as nexus, in states you never set foot in as an owner. Run the apportionment math and the residency-audit rules (most high-tax states audit leavers aggressively) with a CPA before signing anything. The flat-tax state still wants you; it just wants you with full information.
5. Time income around scheduled cuts where you honestly can. When a rate drop is already signed into law — Mississippi's annual steps down are the clearest example — cash-basis businesses can legitimately shift some income into the lower-rate year by timing invoices, bonuses, and equipment purchases. Accrual-basis businesses have less room, and revenue-triggered cuts that have not yet fired should be treated as possibilities, not promises. Never let the tax tail wag the business dog: a discount for early customer payment usually beats a 1-point rate saving.
Keep Multi-State Books Clean From Day One
Every item on that checklist gets easier or harder depending on one thing: whether your books can tell you, state by state, where each dollar was earned and each expense was incurred. Apportionment formulas, estimated-payment calculations, pass-through entity tax filings, and residency-audit defenses all run on the same raw material — clean, contemporaneous records tagged by jurisdiction. The owners who scramble every March are rarely the ones with complicated businesses; they are the ones whose books lump three states of activity into one undifferentiated pile and hope the CPA can sort it out.
Tag revenue and direct expenses by state as you go, keep a simple log of where work is performed and where employees sit, and reconcile estimated payments against actual liability quarterly instead of annually. The Beancount documentation shows how to model multi-dimensional tracking as plain-text transactions you can audit line by line, which is exactly the structure a multi-state operation needs.
Simplify Your Multi-State Bookkeeping
As the flat-tax wave keeps redrawing the map — new rates nearly every January, phase-ins tied to revenue triggers, and pass-through elections with unforgiving deadlines — keeping each state's income, payments, and filings in one consistent ledger is what turns lower rates into actual savings. Beancount.io provides plain-text accounting that gives you complete transparency and control over your financial data — no black boxes, no vendor lock-in. Get started for free and see why developers and finance professionals are switching to plain-text accounting.
