Roughly 20% to 35% of an Iowa paycheck disappears to taxes before it reaches your bank account, and the exact share depends on your income and filing status. Four deductions do almost all the work: federal income tax, Social Security at 6.2%, Medicare at 1.45%, and Iowa’s flat 3.8% state income tax. Knowing how much tax is deducted from your Iowa paycheck, and why each line is the size it is, lets you catch payroll mistakes and adjust your withholding before April.
Federal Income Tax: The Biggest Line
Federal income tax is typically the largest single deduction on your stub. Your employer calculates it from the information on your IRS Form W-4: filing status, whether you hold multiple jobs, any dependents, and any extra amount you asked to have withheld.1Internal Revenue Service. Topic No. 753, Form W-4, Employee’s Withholding Certificate
The federal system is progressive, so different slices of your income are taxed at different rates. For 2026, a single filer pays 10% on income up to $12,400, 12% on income up to $50,400, 22% up to $105,700, and 24% up to $256,225, with higher rates above that. For married couples filing jointly, each threshold roughly doubles: the 10% bracket runs to $24,800, the 12% bracket runs to $100,800, and the top 37% rate applies above $768,700.2Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026
Your employer doesn’t apply those brackets to your full gross pay. Wages are first reduced by any pre-tax deductions and by the standard deduction amount built into the withholding tables. For 2026, that standard deduction is $16,100 for single filers and $32,200 for married couples filing jointly.2Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026
Social Security and Medicare (FICA)
The next two lines are fixed by statute, and no W-4 election changes them.
Social Security is 6.2% of your gross wages, but only up to the 2026 wage base of $184,500. Once your year-to-date earnings hit that ceiling, Social Security withholding stops for the rest of the year. If you earn $184,500 or more, your maximum Social Security contribution for 2026 is $11,439.3Social Security Administration. Contribution and Benefit Base
Medicare is 1.45% on all wages, with no cap. Your employer pays a matching 1.45%, but that side doesn’t appear on your stub because it isn’t your obligation.4Internal Revenue Service. Topic No. 751, Social Security and Medicare Withholding Rates
An Additional Medicare Tax of 0.9% kicks in once your wages exceed $200,000 in a calendar year. Your employer starts withholding it automatically at that point, regardless of your filing status. The actual liability threshold on your return varies: married couples filing jointly owe it above $250,000 in combined wages, and married individuals filing separately owe it above $125,000. Any difference gets reconciled when you file. Employers do not match the 0.9%; that piece is entirely on you.5Internal Revenue Service. Questions and Answers for the Additional Medicare Tax
Iowa State Income Tax at 3.8%
Iowa’s state income tax is simpler than the federal system. Since 2025, Iowa has charged a flat 3.8% on all taxable individual income, replacing the graduated brackets the state used for decades. That rate stays at 3.8% for 2026.6Iowa Department of Revenue. IDR Announces 2026 Individual Income Tax and Interest Rates
Your employer doesn’t just multiply your gross pay by 3.8%. The Iowa Department of Revenue’s withholding formula first subtracts allowances based on your filing status and the information you reported on your IA W-4. The 3.8% rate then applies to what’s left, your taxable wages for state purposes.7Iowa Department of Revenue. Iowa Withholding Tax Information
Because the rate is flat, the math is straightforward once you know your allowance amount. Iowa’s line is usually one of the more predictable numbers on your stub.
What You Won’t See on Your Stub
Iowa does not impose a local income tax on wages, so no city or county tax line appears on your paycheck. Some Iowa localities charge a local option sales tax, but that hits you at the register, not through payroll.
State Unemployment Insurance is a payroll tax in Iowa, but your employer pays the full amount, so you won’t see an SUI line on your stub.8Justia. Iowa Code 96.7 – Employer Contributions and Reimbursements Iowa also has no state disability insurance or paid-leave payroll tax that comes out of employee wages. For most workers, the tax section of the stub is exactly four lines: federal income tax, Social Security, Medicare, and Iowa state income tax.
How Pre-Tax Deductions Shrink the Bill
Voluntary deductions like traditional 401(k) contributions, health insurance premiums, and Health Savings Account deposits often come out of your paycheck before taxes are calculated. That reduces the income subject to both federal and Iowa state income tax withholding, so your tax lines are smaller with each check.
FICA treatment varies by deduction type. Traditional 401(k) contributions reduce your federal and state taxable income but are still subject to Social Security and Medicare. HSA contributions made through payroll are exempt from FICA as well. The distinction matters if you’re close to the Social Security wage base or trying to estimate your total tax burden precisely.
Roth 401(k) contributions come out after income tax is calculated, so they don’t reduce your current withholding. The trade-off is tax-free withdrawals in retirement. Either way, these deductions appear in a separate section of your stub from the mandatory taxes.
Crossing the Iowa-Illinois Border
Iowa has one reciprocal tax agreement, and it’s with Illinois. If you live in Iowa but commute to an Illinois job, your wages are taxable only to Iowa. Your Illinois employer should withhold Iowa tax rather than Illinois tax, but you have to file Illinois Form IL-W-5-NR with that employer to make it happen, and submit an Iowa W-4 so the correct Iowa withholding applies.9Iowa Department of Revenue. Iowa – Illinois Reciprocal Agreement
The reverse is true for Illinois residents working in Iowa; those wages are taxable only to Illinois. Those employees file Iowa Form 44-016 with their Iowa employer to avoid Iowa withholding.9Iowa Department of Revenue. Iowa – Illinois Reciprocal Agreement The agreement covers only wages and salaries. Iowa gambling winnings and Iowa unemployment compensation are not covered.
Adjusting Your Withholding
Two forms control how much tax comes out of your Iowa paycheck: the federal W-4 and the Iowa IA W-4. You can update either one at any time by submitting a new version to payroll.10Iowa Department of Revenue. Withholding Frequently Asked Questions
The federal W-4 asks for your filing status, whether your spouse works, the number of dependents you’re claiming, and any additional amount you’d like withheld per pay period. If you have multiple jobs or significant non-wage income, Step 2 and Step 4 of the form help your employer account for that.11Internal Revenue Service. Form W-4 2026 – Employee’s Withholding Certificate
The Iowa IA W-4 works similarly but is specific to state withholding. It uses an allowances approach tied to your marital status, dependents, and any Iowa credits you expect to claim, such as the Child and Dependent Care Credit. If you don’t file an IA W-4, your employer must withhold at an allowance amount of zero, which usually means more state tax comes out than necessary.7Iowa Department of Revenue. Iowa Withholding Tax Information
Life changes that should prompt a fresh W-4 include getting married, having a child, picking up a second job, or landing a large raise. Each of these shifts your annual tax liability enough that your old settings may leave you owing money or over-withholding for months.
Checking Your Stub and Running the Numbers
Iowa law requires your employer to give you a statement each payday showing your hours, wages, and deductions. If you want more detail, you can submit a written request and the employer must provide an itemized breakdown of earnings and deductions within ten working days, along with an explanation of how those numbers were calculated.12Iowa Legislature. Iowa Code 91A.6 – Notice and Recordkeeping Requirements
When you review a stub, verify that federal income tax, Social Security, Medicare, and Iowa state income tax each appear as separate lines. Confirm that Social Security is exactly 6.2% of your gross pay, or has stopped if you’ve hit the $184,500 cap, that Medicare is 1.45%, and that Iowa state tax looks roughly proportional to 3.8% of your taxable wages. Flag anything odd to payroll, especially withholding that didn’t change after you submitted a new W-4, or Social Security still being deducted after you’ve crossed the wage base.
The IRS Tax Withholding Estimator walks you through your income, deductions, and credits and tells you whether your federal withholding is on track.13Internal Revenue Service. Tax Withholding Estimator The Iowa Department of Revenue provides its own online withholding calculator for state taxes, on its withholding guidance page.7Iowa Department of Revenue. Iowa Withholding Tax Information Running both once or twice a year, and after any major life change, is the most reliable way to keep the numbers on your stub matching what you’ll actually owe.