Tax deducted at source is the system in which the person or business paying you income holds back a portion of that payment and sends it directly to the IRS on your behalf, so the tax is collected before the money ever reaches you. In the United States it takes three main forms: federal income and payroll tax withheld from your paycheck, backup withholding on certain non-wage payments like contractor fees and interest, and a flat 30% withheld from most U.S.-source income paid to foreign persons. The mechanism keeps revenue flowing to the Treasury throughout the year rather than depending on one lump-sum payment each April.
Withholding From Your Paycheck
Federal law requires every employer paying wages to deduct and withhold income tax before handing over the paycheck.1Office of the Law Revision Counsel. 26 USC 3402 – Income Tax Collected at Source How much comes out depends on your pay, your filing status, and what you put on Form W-4. Your employer runs those inputs through IRS withholding tables, deposits the tax with the Treasury on a regular schedule, and reports the year’s totals on the Form W-2 you receive in January.
The goal is to land close to your actual tax bill across the year. Get it right and you owe little and are refunded little. Get it wrong in either direction and you’ll notice at tax time.
On top of income tax, your employer also withholds FICA taxes to fund Social Security and Medicare. These are split evenly between you and your employer:
- Social Security: 6.2% of wages, up to a wage base of $184,500 in 2026. Once you hit the cap, Social Security withholding stops for the rest of the year.2Social Security Administration. Contribution and Benefit Base
- Medicare: 1.45% of all wages, no cap.3Office of the Law Revision Counsel. 26 USC 3101 – Rate of Tax
- Additional Medicare Tax: an extra 0.9% on wages above $200,000 in a calendar year, withheld by the employer without a matching employer share. The $200,000 trigger applies regardless of filing status for withholding purposes, though your actual liability threshold on the return differs for joint and separate filers.4Internal Revenue Service. Additional Medicare Tax
FICA rates are set by statute. You can’t reduce them with a form, and your employer has no discretion to change them. If you work more than one job and your combined wages exceed the Social Security wage base, you may overpay Social Security across employers; you claim the excess back on your annual return.
Controlling Your Income Tax Withholding With Form W-4
Form W-4 is how you tell your employer how much federal income tax to withhold.5Internal Revenue Service. Form W-4 – Employee’s Withholding Certificate You complete one at a new job, and you can submit a new one whenever your situation changes.
Step 1 captures filing status. Step 2 matters when you hold more than one job or your spouse also works, because the default calculation assumes a single job. Step 3 lets you reduce withholding for dependents: $2,200 per qualifying child under 17 and $500 per other dependent, available if you earn $200,000 or less ($400,000 for joint filers).6Internal Revenue Service. Child Tax Credit Step 4 handles extra income outside your job, deductions beyond the standard deduction, and any additional flat amount you want pulled from each check.
Two mistakes trip people up. Adding a second job (or a working spouse) without updating Step 2 almost guarantees underwithholding. Overclaiming in Step 3 does the same. The IRS Tax Withholding Estimator runs the actual math for your situation and is worth using at least once a year.
If you had no federal tax liability last year and expect none this year, you can claim exemption from withholding altogether. That exemption expires every February and must be renewed.
Backup Withholding on Contractor Pay, Interest, and Dividends
Backup withholding is a separate mechanism aimed at non-wage payments: interest, dividends, and payments to independent contractors, among others. The rate is a flat 24%.7Internal Revenue Service. Publication 15 (2026) – Employer’s Tax Guide It kicks in when the normal reporting chain breaks, usually because the payer doesn’t have a valid taxpayer identification number on file for the payee.
A payer must start backup withholding when any of the following happens:8Office of the Law Revision Counsel. 26 USC 3406 – Backup Withholding
- The payee never furnished a TIN, or the number provided has the wrong number of digits.
- The IRS notifies the payer that the name and TIN combination doesn’t match its records.
- The IRS notifies the payer that the payee has been underreporting interest or dividend income.
- The payee didn’t properly certify their TIN on Form W-9.
This is what Form W-9 is for. When a business hires a contractor or opens an account that will generate reportable payments, it collects a completed W-9 to capture the payee’s name and TIN. Providing a valid W-9 is the simplest way to avoid the 24% deduction.9Internal Revenue Service. Backup Withholding “B” Program
One change for 2026 matters here: the reporting threshold for payments to independent contractors on Form 1099-NEC rose from $600 to $2,000. A payer doesn’t need to file a 1099-NEC (or apply backup withholding on those payments) unless total payments to a single payee reach $2,000 in the calendar year. The threshold will adjust for inflation starting in 2027.7Internal Revenue Service. Publication 15 (2026) – Employer’s Tax Guide
Withholding on Payments to Foreign Persons
When a U.S. payer sends certain kinds of income to a foreign individual or entity, federal law requires withholding at a flat 30%.10Office of the Law Revision Counsel. 26 USC 1441 – Withholding of Tax on Nonresident Aliens The scope is broad: interest, dividends, rent, royalties, compensation for services, and other recurring U.S.-source payments.11Internal Revenue Service. Withholding on Specific Income
Tax treaties between the U.S. and dozens of countries can reduce or eliminate that 30% rate for treaty-country residents. To claim a lower rate, the foreign recipient files Form W-8BEN (individuals) or W-8BEN-E (entities) with the payer. Without a valid form on file, the payer must withhold the full 30%. Payments and withholdings are reported on Form 1042-S, with an annual Form 1042 return. The payer is personally liable for any tax that should have been withheld but wasn’t.
State Income Tax Withholding
Most states also impose income tax and require employers to withhold it alongside federal tax, using their own rates and forms. Nine states have no income tax and no withholding requirement: Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas, Washington, and Wyoming. If you live in one state and work in another, you may face withholding in both, though many neighboring states have reciprocity agreements that simplify the split. State tax withheld functions as a prepayment on your state return, the same way federal withholding does on Form 1040.
What Happens at Tax Time
Withholding is an estimate. Your real tax bill depends on your full-year income, deductions, and credits, none of which your employer knows precisely in real time. The reconciliation happens on your annual return.
If more was withheld than you owe, the difference comes back as a refund when you file Form 1040. If you discover the overpayment after filing, you can amend on Form 1040-X. The IRS generally gives you three years from the date you filed the original return, or two years from when you paid the tax, whichever is later, to claim that money.12Internal Revenue Service. Time You Can Claim a Credit or Refund Miss that window and the refund is gone.
If too little was withheld, you owe the balance when you file and may face an underpayment penalty on top. The IRS charges interest on the shortfall for each quarter it went unpaid. You avoid the penalty if your balance due is under $1,000, or if your withholding and estimated payments covered at least 90% of this year’s tax or 100% of last year’s tax (110% if your adjusted gross income was above $150,000).13Internal Revenue Service. Underpayment of Estimated Tax by Individuals Penalty The prior-year safe harbor is the practical one to aim for: match last year’s total tax through withholding and you’re protected no matter how much your income climbed.