The difference between federal and state taxes comes down to who taxes what: the federal government relies mostly on income and payroll taxes collected by the IRS, while states draw revenue from a mix of income taxes, sales taxes, and property taxes administered by their own agencies under their own rules. Nine states skip personal income tax entirely, and the calculations at each level rarely produce the same taxable income even when they start from the same paycheck.
What Each Level of Government Taxes
The federal government funds itself primarily through two channels. Individual and corporate income taxes go to the IRS through Form 1040 and corporate returns. Payroll taxes for Social Security and Medicare come out of every paycheck and account for roughly one-third of all federal revenue.1Tax Foundation. The Federal Payroll Tax: A Primer Federal excise taxes exist too, but they hit manufacturers rather than consumers directly. Buy tires, firearms, or certain fuels, and the excise tax was baked into the price before the product reached the shelf.2Office of the Law Revision Counsel. 26 U.S.C. Subtitle D, Chapter 32 – Manufacturers Excise Taxes
States cast a wider net. Most collect their own income tax, but the bigger collective revenue driver across all states is sales tax, charged at the register on most goods and some services. Combined state and local sales tax rates range from zero in a handful of states to over 10% in the highest jurisdictions. States also impose excise taxes on gasoline, tobacco, and alcohol, often earmarked for road maintenance or public health. Property taxes are collected locally but authorized and regulated under state law. The federal government has no counterpart to sales tax or property tax.
How Income Tax Compares at Each Level
Federal income tax runs on a progressive structure with seven brackets, so the rate climbs as income crosses each threshold. You don’t pay the top rate on every dollar earned; each bracket applies only to the income falling within its range.3Internal Revenue Service. Federal Income Tax Rates and Brackets The rates run from 10% at the bottom to 37% at the top. For 2026, a single filer hits the top 37% bracket at income above $640,600, while married couples filing jointly don’t reach it until $768,700.4Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026, Including Amendments from the One, Big, Beautiful Bill
Before those rates apply, you reduce income by the standard deduction or by itemizing on Schedule A.5Internal Revenue Service. About Schedule A (Form 1040), Itemized Deductions For 2026, the standard deduction is $32,200 for married couples filing jointly, $16,100 for single filers, and $24,150 for heads of household.4Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026, Including Amendments from the One, Big, Beautiful Bill Most taxpayers take the standard deduction because it exceeds what they could claim by itemizing.
The federal system also treats long-term capital gains differently. Hold an investment more than a year before selling and the profit is taxed at 0%, 15%, or 20% depending on income, rather than at ordinary income rates.
State income taxes look nothing alike from one state to the next. Nine states impose no personal income tax at all. Among states that do tax income, about 14 use a flat rate, taxing all income at a single percentage. The rest run their own progressive brackets, typically fewer and lower than the seven federal tiers. Top rates in the highest-tax states exceed 10%.
Most states simplify things by using federal adjusted gross income as the starting point on the state return. You copy that number from your Form 1040, and the state applies its own adjustments. Some states add back income exempt federally, like interest from another state’s bonds. Others offer deductions that don’t exist federally, such as credits for local property taxes paid or contributions to a state-sponsored college savings plan. The result is that state taxable income is almost never the same number as federal taxable income, even though both start from the same AGI.
Capital gains is where the split shows up starkly. Most states tax long-term gains as ordinary income with no preferential rate. So while the federal government might charge 15% on a stock sale, your state could charge its full income tax rate on the same gain.
Payroll and Self-Employment Taxes
Payroll taxes are almost entirely a federal obligation. If you work for an employer, your paycheck shows two federal withholdings beyond income tax: 6.2% for Social Security and 1.45% for Medicare. Your employer matches both amounts. For 2026, Social Security tax applies only to the first $184,500 in wages; anything above that is exempt from the 6.2% charge.6Social Security Administration. 2026 Cost-of-Living Adjustment (COLA) Fact Sheet Medicare has no cap, and high earners pay an additional 0.9% Medicare surtax on wages above $200,000, or $250,000 for married couples filing jointly.
Self-employed workers pay both halves, a combined 15.3% on net earnings up to the Social Security wage base.6Social Security Administration. 2026 Cost-of-Living Adjustment (COLA) Fact Sheet Half of that amount is deductible on the federal return, but it’s still one of the largest tax bills self-employed people face.
States generally do not impose their own equivalents of Social Security or Medicare. A handful collect payroll-based contributions for state disability insurance or paid family leave, but these are much smaller in scale than federal FICA.
Sales, Property, and Excise Taxes
There is no federal sales tax and no federal property tax. These revenue streams belong entirely to state and local governments.
Sales taxes are the most visible state-level tax for most people. Five states charge no state-level sales tax, while others approach or exceed 10% when local taxes are added. What’s subject to sales tax also varies by state: some tax groceries and clothing, others exempt them.
Property taxes are assessed by local governments under authority granted by state law. Assessed value, tax rate, and any homestead exemptions are all set at the state and local level. They fund public schools and local services. The federal government has no role in setting or collecting them.
Both levels of government collect excise taxes, but they target different things. Federal excise taxes are embedded in the wholesale price of goods like fuel, tires, and firearms.2Office of the Law Revision Counsel. 26 U.S.C. Subtitle D, Chapter 32 – Manufacturers Excise Taxes State excise taxes on gasoline, tobacco, and alcohol are charged per unit and vary widely. State gas taxes range from under $0.09 per gallon to over $0.70 per gallon, with federal taxes added on top.
Where the Two Systems Connect
Federal and state taxes aren’t calculated in isolation. Several mechanisms link them, and understanding those links can save money or prevent paying tax on the same income twice.
The SALT Deduction
The most direct connection is the state and local tax (SALT) deduction on the federal return. If you itemize, you can subtract state income taxes (or sales taxes, but not both), plus property taxes, from federal taxable income.7Office of the Law Revision Counsel. 26 U.S.C. 164 – Taxes
The Tax Cuts and Jobs Act of 2017 capped this deduction at $10,000 ($5,000 for married filing separately), which hit residents of high-tax states hard. The One Big Beautiful Bill Act, signed in 2025, raised that cap substantially. For 2026, the SALT deduction limit is $40,400, with a $20,000 cap for married individuals filing separately. The cap increases by 1% annually through 2029.
The higher cap phases out for high earners. In 2026, the phaseout begins at a modified adjusted gross income of $505,000 ($250,000 for married filing separately). Once income exceeds roughly $606,000 ($300,000 for married filing separately), the cap drops back to $10,000. The expanded deduction primarily benefits middle- and upper-middle-income taxpayers in high-tax states, not the highest earners.
Working Across State Lines
When you live in one state and work in another, both states could theoretically tax the same wages. Your home state typically taxes all your income regardless of where it’s earned, and the work state taxes income earned within its borders. To prevent double taxation, your home state gives you a credit for taxes paid to the work state. You still end up paying the higher of the two state rates, but not both in full. This requires filing returns in both states and attaching proof of taxes paid.
Some neighboring states have reciprocal agreements that simplify this entirely. Under a reciprocal agreement, the work state doesn’t withhold its income tax, so you only file and pay in your home state. These agreements are concentrated in the Midwest and along the East Coast.
Residency itself is determined by two main tests. Domicile is your permanent home, the place you intend to return to even when away. Statutory residency is based on physical presence, and most states that use this test set the threshold at around 183 days. You can be a domiciliary of one state and a statutory resident of another, which creates the risk of two states claiming you as a full resident. People who split time between two states need to track their days carefully.
Pass-Through Entity Tax Elections
After the 2017 SALT cap took effect, more than 30 states created a workaround for business owners. A pass-through entity tax (PTET) lets an S-corporation, partnership, or LLC elect to pay state income tax at the entity level rather than passing all the income through to owners’ personal returns. Because the entity-level tax is treated as a business expense, it’s fully deductible on the federal return, bypassing the individual SALT cap. Owners then receive a state credit that offsets their personal state liability. The net state tax bill stays the same, but the federal deduction is restored.
Filing With Two Separate Agencies
You deal with two entirely separate bureaucracies. The IRS handles the federal return, and your state’s department of revenue (or taxation, depending on the state) handles the state return. Each has its own forms, deadlines, and enforcement powers.
Most states set their filing deadline to match the federal April 15 date, but not all do. State extension rules are a common trap. Getting a federal extension doesn’t automatically extend the state deadline everywhere. Some states grant the extension automatically if you have a federal one; others require a separate state extension form or at least a notation on the return. Missing the state deadline triggers penalties that accrue independently of anything happening on the federal side.
Federal penalties for late payment run 0.5% of the unpaid balance per month, capped at 25%.8Internal Revenue Service. Failure to Pay Penalty Interest on the unpaid balance compounds daily at 7% annually as of early 2026.9Internal Revenue Service. Interest Rates Remain the Same for the First Quarter of 2026 State penalty and interest rates vary, and some states charge more aggressively than the IRS. Each system’s penalties are independent, so underpaying both governments means two separate penalty calculations running at the same time.
The two systems share information. The IRS and state tax agencies have data-sharing agreements, and a federal audit that changes your AGI almost always triggers a state adjustment, since most states use federal AGI as their starting point. Some states require you to file an amended state return within a set number of days after a federal change. A state audit rarely triggers an IRS review, because state-specific adjustments to credits or deductions usually have no federal impact. The state’s ability to place liens on property, garnish wages, and assess penalties operates entirely separately from the IRS’s collection authority.