What is Form W-4?
Form W-4 is the IRS form you fill out when starting a new job (or when your tax situation changes) to tell your employer how much federal income tax to withhold from each paycheck. It accounts for filing status, dependents, multiple jobs, and any additional voluntary withholding.
Full explanation
Form W-4 (Employee's Withholding Certificate) is the federal income-tax withholding form. The employer uses your W-4 inputs — filing status, claimed dependents, multiple-jobs adjustment, additional withholding amount — together with the IRS withholding tables to calculate the federal tax line on each paystub.
The 2020+ W-4 redesign removed the old "allowances" concept. Instead, you enter direct dollar amounts: dependents (multiply $2,000 per qualifying child under 17, or $500 per other dependent), other income not from jobs, deductions beyond the standard deduction, and any extra amount you want withheld per pay period.
You should update your W-4 after major life changes: marriage or divorce (filing status), having or adopting a child (dependents), starting or ending a second job, large income changes (raise, bonus pattern shift, or spouse's job change), or moving to a state with different tax rules. The IRS publishes a Tax Withholding Estimator at irs.gov that helps you check whether your current W-4 is producing the right withholding.
Common mistakes: claiming too many dependents (under-withholds, big tax bill in April); not accounting for a spouse's job (couples filing jointly often need the "multiple jobs" step or the higher withholding tables); forgetting to update after a raise (under-withholds at the new income level). Reviewing your W-4 each January is a useful habit.
Frequently asked questions about Form W-4
When do I need to fill out a W-4?
When starting a new job (your employer will give you one), and any time your tax situation materially changes — marriage, divorce, new dependent, second job, large income change, or moving to a state with different tax rules.
What replaced the old "allowances" on the W-4?
The 2020+ W-4 uses direct dollar amounts instead. You enter dollar values for dependents, other income, deductions, and any extra per-paycheck withholding — no more counting allowances and looking up corresponding amounts.
Where can I find my current W-4 election?
Most employers expose your current W-4 settings through the employee pay portal or HR system. If not, ask HR or payroll directly. You can submit an updated W-4 at any time; the new election takes effect on the next pay period after processing.