State Income Tax Withholding

State income tax withholding is the portion of an employee's pay that an employer deducts and sends to a state tax agency as a prepayment of the employee's state income tax. It runs alongside federal income tax withholding, but follows each state's own rules.

Withholding is not one national system. States set their own forms, rates and deadlines, and some states do not tax wages at all.

How Does State Withholding Differ From Federal Withholding?

Federal withholding follows the W-4 form and IRS tables. States run separate systems. Florida does not impose a personal income tax, so employers there have no state income tax to withhold, while states such as California and Illinois tax wages.

Rate design varies. Illinois uses a flat 4.95% rate with a $2,925 exemption allowance for 2026. California uses graduated withholding schedules that rise from 1.1% to 14.63% in 2026.

What Forms and Registration Do Employers Need?

Some states publish their own withholding certificate. California says employers must use the DE 4 when an employee provides one, and Illinois employers collect Form IL-W-4. With no properly completed DE 4 and no valid earlier certificate, California employers withhold as if the employee were single with zero allowances.

Employers must also register before withholding. Illinois requires you to register and report your payroll start date. California requires registration within 15 days of paying more than $100 in wages in a quarter.

Which State Withholds When an Employee Lives in Another State?

Work location usually drives withholding. Illinois requires withholding on compensation paid in Illinois, and California subjects a nonresident's California-earned wages to California withholding, based on the share of working days there.

Residency adds a second claim. Illinois tells employers they may also have to withhold for another state where the employee works or lives. Employers need not withhold Illinois tax for an Illinois resident who works entirely in another state that requires withholding.

A few state pairs have reciprocity agreements that change this, so confirm each state's revenue page before withholding.

How Do Supplemental Pay, Deposits and the W-2 Work?

Bonuses can carry their own method. California lets employers withhold 10.23% on bonuses and stock options and 6.6% on other supplemental wages paid separately from regular pay. Other states set their own approach.

Deposit schedules vary too. New Illinois registrants start on a monthly payment and quarterly return schedule, while California ties deposit dates to the employer's federal deposit schedule and accumulated withholding.

On Form W-2, boxes 15 through 17 carry the state, employer state ID, state wages and state income tax. One form fits two states, so a third state needs a second W-2.

How Does HR Cloud Help With State Withholding?

HR Cloud's multi-state compliance guide says it handles the HR and compliance layer and integrates with payroll systems that handle tax filing. For ADP Workforce Now, it says the standard connector exports state tax forms and W-4s.

The payroll integration and People HRIS pages do not describe state withholding calculation, so keep that in payroll. Request a demo to see the employee record.

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Frequently Asked Questions

Q: Can an employee claim exemption from state withholding?

A: Rules vary by state. In California, an exempt DE 4 is valid only for the calendar year, and the employee must file a new one by February 15.

Q: Is the employer liable if it fails to withhold?

A: Yes. Illinois says a withholding agent is liable for taxes it is required to withhold, and amounts required to be withheld, plus penalties and interest, are considered a tax on the employer.

Q: What records support withholding for traveling employees?

A: In Illinois, a nonresident paid for more than 30 working days in the state completes Form IL-W-6, unless the employer's time system records daily work location and allocates wages by state.

Q: Does withholding equal the tax an employee owes?

A: No. It is a prepayment. Illinois notes that residents who work in other states may need estimated payments if the credit for the other state's tax does not cover Illinois tax.

Q: How is a bonus taxed when paid with regular wages?

A: California combines it with regular wages and uses the regular PIT schedules. The flat supplemental rates apply only when the bonus is paid separately.

Q: Where does local income tax appear on the W-2?

A: Boxes 18 through 20 hold local wages, local income tax and locality name. The IRS tells employers to contact their state or locality for specific reporting information.