Federal and state income tax withholding is the largest deduction for most workers, and the amount withheld depends on three things: your gross pay, your W-4 elections, and the tax brackets in effect for the year. Your employer uses IRS withholding tables and your state's equivalent to estimate what you will owe in April, then takes that amount out of each paycheck so you do not face a large bill at tax time.
How federal income tax withholding works
The United States uses a progressive tax system, meaning your income is taxed in layers. For 2025, the first portion of your taxable income is taxed at 10%, the next portion at 12%, and so on up to 37% for income above approximately $609,000 for single filers. Your employer does not know your total annual income in advance, so the W-4 form you filled out when you were hired tells them how much to withhold per paycheck. Claiming zero allowances withholds the most; claiming one or two reduces withholding. The 2020 redesign of the W-4 replaced allowances with a step-by-step worksheet that accounts for multiple jobs, dependents, and other income, making withholding more accurate but also more complex to fill out.
State income tax withholding
Forty-one states and the District of Columbia levy an income tax; nine states — Alaska, Florida, Nevada, South Dakota, Tennessee, Texas, Washington, and Wyoming — do not. State tax rates range from under 3% in Pennsylvania and Indiana to over 13% in California for high earners. Most states use their own withholding certificate (the state equivalent of a W-4), and your employer withholds based on that form and the state's brackets. A few states use a flat rate on all income, which simplifies the calculation. If you live in one state and work in another, your employer typically withholds for the work state, and you file a nonresident return there plus a resident return in your home state, claiming a credit for tax paid to the other state.
Why your withholding might be wrong
Withholding is an estimate. If you have income your employer does not know about — freelance income, investment gains, a second job — your withholding will be too low and you will owe in April. If you claimed too few allowances or your circumstances changed (you got married, had a child, bought a house), your withholding may be too high and you will get a refund. The IRS publishes a withholding estimator at irs.gov that walks you through your actual situation and tells you whether to submit a new W-4. Running that estimator once a year, especially after a major life event, keeps your withholding accurate and your paychecks predictable.
Adjusting your W-4 to control take-home pay
If you consistently get a large refund, you are giving the government an interest-free loan. You can increase your take-home pay by submitting a new W-4 that reduces withholding — claim an additional dependent or enter an amount on line 3 (the extra income you expect, which lowers withholding per check). If you usually owe in April, do the opposite: enter an additional withholding amount on line 4c so more is taken out each pay period. Your employer must implement a new W-4 within 30 days, and you can update it as often as you like. Mora's AI companion can walk you through the logic of adjusting withholding based on your actual spending and savings goals, so you're not guessing.
