14 US states have a single flat income tax rate for all earners. Rates range from Arizona's 2.5% (lowest) to Idaho's 5.8% (highest).
Fourteen US states use flat income tax in 2026: Arizona (2.5%), Colorado (4.4%), Georgia (5.39%), Idaho (5.8%), Illinois (4.95%), Indiana (3.05%), Kentucky (4.5%), Louisiana (3%), Massachusetts (5% + 4% millionaire surtax), Michigan (4.25%), Mississippi (4.7%), North Carolina (4.5%), Pennsylvania (3.07%), and Utah (4.65%). High earners save the most in Arizona, Indiana, and Pennsylvania—the lowest-rate states. Low earners often pay more than they would under progressive brackets.
As of 2026, 14 US states use a flat income tax system—meaning all residents pay the same tax rate regardless of income. Flat tax rates range from Arizona's 2.5% (the lowest state income tax in the nation) to Idaho's 5.8%. Unlike progressive tax states (like California with 9 brackets up to 13.3%), flat tax states offer simplicity: you calculate tax by multiplying your income by a single rate. This guide covers all 14 flat tax states, compares rates side-by-side, explains who benefits most, and breaks down the pros and cons of flat tax systems.
Fourteen states use flat income tax: Arizona (2.5%), Colorado (4.4%), Georgia (5.39%), Idaho (5.8%), Illinois (4.95%), Indiana (3.05%), Kentucky (4.5%), Louisiana (3%), Massachusetts (5% + 4% millionaire surtax), Michigan (4.25%), Mississippi (4.7%), North Carolina (4.5%), Pennsylvania (3.07%), and Utah (4.65%). Arizona has the lowest rate; Idaho has the highest.
Arizona has the lowest flat income tax rate in the nation at 2.5%. A $100,000 earner pays just $2,500 in state income tax. This is lower than all other flat tax states and significantly lower than progressive tax states like California (where $100K = $6,266 tax).
Not always. Some flat tax states (Illinois, Pennsylvania, Michigan) have high property taxes that offset the income tax benefit. Illinois has 4.95% income tax but the 2nd highest property tax (2.08%) in the nation. Total tax burden matters more than income tax alone. Arizona, Indiana, and Utah have low overall tax burdens. Illinois and Pennsylvania do not.
High earners in LOW flat tax states benefit most. A $500K earner in Arizona (2.5%) pays $12,500 vs $47,823 in California (progressive 13.3% top rate)—a $35,323 annual savings. Low earners often pay MORE in flat tax states than they would in progressive states with 0% bottom brackets.
It depends on your definition of fair. Proponents say flat taxes are fair because everyone pays the same percentage. Critics say flat taxes are regressive because 4.5% of a $40K salary ($1,800) is a bigger sacrifice than 4.5% of a $400K salary ($18,000). Progressive brackets charge low earners 0-2%, reducing burden on those least able to pay.
Pennsylvania and Indiana are best for retirees. Pennsylvania exempts ALL retirement income (pensions, Social Security, IRA/401k withdrawals) from state tax. Indiana partially exempts retirement income and has a low 3.05% rate. A retiree with $80K in pension income pays $0 in Pennsylvania vs $4,000+ in most other states.
Yes, but it's difficult. Some states (like Illinois and Arizona) have constitutional provisions protecting flat taxes, requiring a voter-approved amendment to switch to progressive brackets. Other states (like Michigan) could change via legislation. However, the trend is toward flat taxes—Louisiana and Mississippi recently switched FROM progressive TO flat.
Massachusetts charges a 5% flat rate on all income, but voters approved a 4% surtax on income over $1 million (effective 2023). This means earners under $1M pay 5% flat, while millionaires pay 9% effective rate on income above $1M. It's technically flat for most people, but progressive at the very top.
States compete for high earners and businesses. Flat taxes (especially low ones like Arizona's 2.5%) attract wealthy residents fleeing high-tax progressive states like California and New York. Arizona, North Carolina, and Louisiana switched to flat taxes to boost population and economic growth. The strategy appears to work—all three saw strong in-migration after the change.
It varies. Some flat tax states (Arizona, North Carolina, Georgia, Michigan) have standard deductions or exemptions that reduce taxable income. Others (Pennsylvania) have NO deductions—you pay the flat rate on every dollar. Check your state's specific rules. Standard deductions make flat taxes less regressive by reducing the burden on low earners.
It depends on your income and the specific state. If you earn $150K+ and move from a high-tax progressive state (CA, NY, NJ) to a low-rate flat tax state (AZ, IN, PA), you'll save thousands per year. But check property taxes, sales taxes, and cost of living. Illinois has a 4.95% flat tax but 2.08% property tax—total burden is higher than many progressive states.
Flat tax states charge a single rate (2.5-5.8%) on all income. No-income-tax states (Alaska, Florida, Nevada, South Dakota, Tennessee, Texas, Washington, Wyoming) charge 0%. No-income-tax states are better for tax savings, but they often offset with higher sales or property taxes. Florida (0% income tax, 0.86% property tax) beats Illinois (4.95% income tax, 2.08% property tax) for most earners.
Last Updated: March 2026