U.S. taxes: federal, state, and local layers explained

U.S. tax law is not one single national brochure: it stacks federal statutes, fifty state regimes, county charters, and city ordinances. This guide frames where to read official sources (IRS, state revenue departments, counties) and how to brief a CPA, EA, or tax attorney.

Dollar thresholds, brackets, and deadlines change every year through legislation and inflation adjustments (Revenue Procedures). Always rely on official publications dated for your tax year — never trust outdated blog posts for dollar amounts.

The federal government levies individual and corporate income taxes (depending on entity type), Social Security and Medicare taxes through FICA, federal unemployment (FUTA) with state credits, excises, and federal estate and gift taxes beyond periodically adjusted exemptions. Each state may add income taxes, sales taxes, fuel taxes, franchise taxes, and other charges. Counties and cities commonly administer property taxes, sometimes local income or wage taxes, hotel occupancy taxes, and targeted fees.

U.S. persons broadly file Form 1040 annually. Gross income includes wages, interest, dividends, net rents, realized capital gains, self-employment income (Schedule C), and certain benefits under specific rules. Marginal brackets and the choice between the standard deduction and itemized deductions change each year — verify using IRS publications or revenue procedures.

Starting points: About Form 1040, Individuals — IRS. Investment income and capital gains follow separate rules (long-term rates, net investment income tax for higher earners — check official thresholds).

Employers withhold federal income tax using the employee's Form W-4 elections (filing status, other jobs, estimated deductions, anticipated credits). Too little withholding can trigger estimated tax requirements (Form 1040-ES) and large April balances. Pay stubs show federal and state withholding; reconcile with year-end Forms W-2 and 1099.

Resources: About Form W-4, Tax Withholding Estimator. See Jobs & Income in the USA.

Employees and employers pay OASDI up to an annual wage base; above that threshold OASDI typically stops for the year. Medicare Hospital Insurance continues without that wage-base cap on ordinary wages, with possible Additional Medicare Tax at higher earnings per IRS guidance.

These amounts appear on pay stubs and Form W-2 — separate from federal income tax withholding. Reference: Social Security and Medicare taxes — IRS.

Self-employment earnings reported on Schedule C generally bear SECA tax, combining employer and employee shares with a statutory deduction for the employer-equivalent portion. Split earners must separate W-2 wages from Schedule C activity.

Official hub: Self-Employed Individuals Tax Center. See Business in the USA.

The AMT is a parallel computation that may apply when deductions or preferences reduce regular tax too far; you pay the greater of regular tax or AMT. Parameters are indexed — follow Form 1040 instructions or certified software. See IRS Topic 556 — AMT.

Taxpayers often choose between the standard deduction and itemized deductions: mortgage interest within limits, state and local taxes subject to federal SALT caps, charitable contributions to qualified organizations, medical expenses beyond AGI floors. State returns may decouple from federal rules.

Helpful publication: Publication 17 — Your Federal Income Tax (updated annually).

C corporations generally file Form 1120; profits can face entity-level tax and dividends shareholder-level tax. Eligible S corporations file 1120-S and issue Schedule K-1 to shareholders. Partnerships file 1065 and issue K-1s. Multi-member LLCs taxed as partnerships follow pass-through mechanics. Sole proprietors report on Schedule C attached to Form 1040.

Estimated taxes often use 1040-ES vouchers. Foreign corporations and controlled foreign corporations may trigger heavy information returns (5471, 8865, etc.) — omissions can carry steep penalties.

Some states impose no general wage income tax (lists and exceptions evolve). Others use progressive or flat rates. Multi-state residency and remote work create sourcing disputes — keep travel logs, domicile records, and employment agreements.

State agency index: taxadmin.org — State tax agencies.

Select cities and school districts levy wage or earned-income taxes within boundaries. Mechanisms differ (credits against state tax may or may not apply). Follow municipal payroll guidance and employer locality codes.

There is no uniform federal VAT like many European countries: retail sales taxes are state and local, often stacked at checkout. Remote sellers must track economic nexus thresholds that vary by state after South Dakota v. Wayfair.

Purchases without collected sales tax may still trigger consumer use tax obligations in your state of consumption — an often-overlooked duty for individuals and small businesses.

Real estate is taxed locally via assessed values and mill rates, often funding schools and services. Homestead exemptions vary. Real estate transfers may trigger documentary or transfer taxes depending on state law — see Real Estate and FIRPTA for nonresident sellers.

Federal and state excises apply to fuels, alcohol, tobacco, trucks, air travel, and telecommunications, among others. Hotels and rental cars often include voter-approved surcharges for tourism or transportation infrastructure.

Federal estate and gift taxes apply beyond inflation-adjusted lifetime exclusions and annual exclusions; several states add inheritance or estate taxes. Amounts change with legislation — verify IRS and state rules for the transfer year. Entry point: Estate tax — IRS.

U.S. tax residency (green card, substantial presence, elections) drives worldwide versus U.S.-source reporting. The U.S.–France income tax treaty may provide relief but requires analysis and proper elections — it does not apply automatically.

FBAR (FinCEN Form 114) reporting for foreign financial accounts above aggregate thresholds and offshore corporate forms carry steep penalties. Banks implement FATCA reporting. An ITIN (Form W-7) serves taxpayers who must file but cannot obtain an SSN. Use qualified cross-border advisors in the U.S. and France (impots.gouv.fr).

Resources: International taxpayers — IRS, Report foreign bank accounts — FinCEN.

April 15 is the usual individual deadline for calendar-year filers when it falls on a business day; a filing extension (Form 4868) extends time to file, not always time to pay — interest and penalties may accrue on unpaid balances.

Quarterly estimated taxes apply to many self-employed taxpayers (typical dates in April, June, September, January — confirm at Estimated taxes — IRS). States set separate deadlines. Disaster declarations may defer IRS due dates for affected counties.

Failure-to-file, failure-to-pay, underpayment of estimates, accuracy-related penalties, and fraud can apply. Interest accrues until paid in full. Voluntary disclosure programs may exist — engage counsel before contacting agencies.