Federal income tax and state income tax are separate obligations with separate rules, separate returns, and separate agencies. Most Americans who owe state income tax must file two returns each year — one with the IRS and one with their state's department of revenue (DOR). The interaction between the two systems can affect how much you owe overall, particularly when you change residence, work across state lines, or move during the year.
How the two systems differ
The federal income tax is administered by the IRS and applies uniformly across all states. Every taxpayer files a Form 1040 (or variant) with the IRS regardless of where they live.
State income taxes are administered by each state's own revenue agency — most commonly called the Department of Revenue or Department of Taxation. Each state sets its own:
- Tax rates and bracket structure (or a flat rate)
- Definition of taxable income (states often start with federal adjusted gross income but then add and subtract their own items)
- Available deductions and credits
- Filing deadlines (often, but not always, aligned with the federal April deadline)
- Residency and source-income rules
Because states write their own rules, the same transaction can be treated very differently at the state level than at the federal level.
States with no income tax
As of this writing, a small number of states impose no individual income tax on wages or salaries. Those states are often listed in IRS and state DOR publications. Note that "no income tax" does not necessarily mean "no state taxes" — many of these states impose higher sales taxes, property taxes, or other levies. And some states that do not tax wages do tax investment income; the details vary and can change with state legislation.
If you live in a no-income-tax state, you still file a federal return but have no state income tax return obligation for that state.
Residency: the foundational question
Your state of domicile — the place you intend to be your permanent home — is generally the state that has the primary right to tax your worldwide income. A state considers you a resident if you:
- Are domiciled there, or
- Maintain a permanent place of abode there and spend more than a set number of days per year (the threshold varies by state)
Changing residency requires more than moving your belongings. States — particularly those with high income taxes — scrutinize moves carefully. You generally need to establish a new domicile (registering to vote, getting a new driver's license, changing your primary banking location, spending the majority of the year in the new state) and sever ties with the old state.
Working in more than one state
If you earn income in a state where you are not a resident, that state may have the right to tax the income earned within its borders. This is called source-based taxation. The practical result:
- You may owe a nonresident return in the state where you worked, reporting only the income earned there.
- Your home state may also tax that income as a resident.
- Most states offer a credit for taxes paid to other states to avoid true double taxation, but the credit calculation is not always a perfect offset.
Remote workers whose employer is in a different state than their home face particularly complex questions — some states assert the right to tax employees based on where the employer's office is located (the "convenience of the employer" rule), regardless of where the employee physically works.
Filing two returns: the practical picture
When you must file in two states, the general process is:
- Complete your federal return first — most state returns start with a federal income figure.
- File a resident return in your home state, reporting all income and claiming credit for any taxes owed to other states.
- File a nonresident return in any other state where you earned source income, reporting only that state's share.
State returns are filed directly with each state's DOR; they are not submitted with or through the IRS.
Common sources of state-federal differences
- Standard deduction: many states have their own standard deduction amounts, which may not match the federal figure.
- Retirement income: some states exempt Social Security, pension, or IRA distributions that are taxable federally.
- Student loan interest, mortgage interest, and charitable deductions: states may allow, cap, or disallow deductions that exist federally.
- Depreciation: states sometimes use different depreciation rules than the federal system.
Where to get help
Multi-state situations, mid-year moves, and remote work arrangements can make state income tax compliance genuinely complicated. A find a tax professional familiar with the states involved can help you understand where you owe, how credits apply, and what documentation you need.
Sources
- IRS Publication 525, Taxable and Nontaxable Income (irs.gov)
- IRS Topic No. 503 and Form 1040 instructions (irs.gov)
- Each state's Department of Revenue or Department of Taxation website (search "[state name] department of revenue")