Every line on your pay stub falls into one of two buckets: voluntary payroll deductions, which come out only because you authorized them in writing, and mandatory payroll deductions, which your employer must withhold under federal, state, or local law or a court order. The difference matters because you control one bucket and not the other. If you want to change your take-home pay, the voluntary side is where the levers are.
Deductions Your Employer Must Take
Mandatory deductions come off your paycheck regardless of your preferences.1eCFR. 29 CFR 3.5 – Payroll Deductions Permissible Without Application to or Approval of the Secretary of Labor Your employer has no discretion, and you can’t opt out through HR.
- Federal income tax. Withheld based on the Form W-4 you filed, including filing status, dependents, and any extra withholding you asked for.2Internal Revenue Service. About Form W-4, Employee’s Withholding Certificate
- Social Security tax. 6.2% of wages, up to a taxable earnings cap of $184,500 in 2026.3Social Security Administration. What is FICA?4Social Security Administration. Contribution and Benefit Base
- Medicare tax. 1.45% on all wages with no cap, plus an additional 0.9% withheld on wages over $200,000 in a calendar year.5Internal Revenue Service. Questions and Answers for the Additional Medicare Tax
- State and local income taxes. Required in most states and in some cities and counties, with rates that vary by jurisdiction.
- Court-ordered garnishments. If a court or agency orders withholding for child support, unpaid taxes, or a creditor judgment, your employer must comply. You cannot stop these through your employer.
Anything else on your stub is voluntary. You authorized it, and you can generally adjust or end it.
Voluntary Deductions You Choose
Voluntary deductions cover benefits, savings, and other perks that only appear on your pay stub because you signed up. The common categories are below.
Retirement Plan Contributions
A 401(k) is the most common example. You defer a portion of salary into an individual retirement account, and you pick the rate.6Internal Revenue Service. 401(k) Plans For 2026, the IRS caps elective deferrals at $24,500. Workers 50 and older can add $8,000 in catch-up contributions, and workers aged 60 through 63 can add $11,250 under SECURE 2.0.7Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500 The same limits apply to 403(b) plans and governmental 457 plans. Smaller employers may offer a SIMPLE IRA instead, funded the same way through payroll but with lower limits.8Internal Revenue Service. SIMPLE IRA Plan
Most plans let you choose between traditional (pre-tax) and Roth (after-tax) contributions, or split the two. The tax treatment is where the choice actually bites, and that’s covered below.
Health Insurance Premiums
If you enroll in your employer’s group health, dental, or vision plan, your share of the premium is a voluntary deduction. Most employers run these through a Section 125 cafeteria plan, which strips the premium out of your wages before federal income tax and before Social Security and Medicare are calculated.9Internal Revenue Service. FAQs for Government Entities Regarding Cafeteria Plans That double tax break is why employer-sponsored coverage is so tax-efficient.
The trade-off is timing. Under IRS rules, you generally can’t change a Section 125 election mid-year unless you have a qualifying life event such as marriage, a birth, or loss of other coverage. Otherwise you wait for open enrollment. Group life, long-term disability, and accident coverages usually work the same way.
HSAs and FSAs
If you’re enrolled in a high-deductible health plan, you can fund a health savings account through payroll. For 2026, the annual limit is $4,400 for self-only coverage and $8,750 for family coverage.10Internal Revenue Service. Revenue Procedure 2025-19 Routed through a cafeteria plan, HSA contributions escape income tax and FICA, and the balance rolls over indefinitely.
A health care flexible spending account also uses pre-tax payroll dollars, capped at $3,400 for 2026, with up to $680 eligible to carry into the next year if your plan allows. You set the amount at enrollment and can only change it after a qualifying life event.
Other Voluntary Deductions
- Employee stock purchase plan contributions, which buy company stock at a discount.
- Union dues, which require written authorization before an employer can withhold and forward them.11U.S. Federal Labor Relations Authority. 5 USC 7115 – Allotments to Representatives
- Charitable contributions through a workplace giving program.
- Repayments on a loan or pay advance from your employer, under the terms of the loan agreement.
- Commuter benefits, parking, and gym memberships.
The through-line is consent. None of these appear on your pay stub without your written say-so.
Pre-Tax vs. Post-Tax Treatment
Voluntary deductions save you different amounts depending on which taxes they bypass, and the differences are larger than most people realize.
Health premiums and HSA contributions run through a Section 125 cafeteria plan are exempt from federal income tax, Social Security tax, and Medicare tax, the full sweep of payroll taxes.9Internal Revenue Service. FAQs for Government Entities Regarding Cafeteria Plans Traditional 401(k) contributions are only exempt from federal income tax. They remain subject to Social Security and Medicare.12Internal Revenue Service. Are Retirement Plan Contributions Subject to Withholding for FICA, Medicare, or Federal Income Tax So a $1,000 traditional 401(k) contribution lowers your income tax withholding but still gets hit with 6.2% Social Security and 1.45% Medicare.
Post-tax deductions come out after every tax is calculated on your full gross pay. Roth 401(k) contributions are the main example: you pay tax now, and qualified withdrawals in retirement come out tax-free.6Internal Revenue Service. 401(k) Plans Union dues, charitable contributions, and ESPP deductions are also post-tax.
Authorizing and Changing Deductions
Your written authorization is what makes a voluntary deduction lawful. Without it on file, withholding money for a voluntary purpose can become an unauthorized wage deduction and expose the employer to a claim. The authorization is usually a signed enrollment form or consent document naming the dollar amount or percentage, the start date, and the destination.
How easy it is to change a deduction depends on the type. Retirement plans are typically the most flexible: many let you change your deferral rate or pause contributions at any time, or at minimum each quarter. Cafeteria plan elections for health premiums and FSAs are locked to open enrollment or a qualifying life event. Loan repayments follow the loan agreement.
To make a change, go to HR or your benefits administrator, get written confirmation the change was processed, and verify it on the next pay stub.
The Minimum Wage Floor
One boundary worth knowing: voluntary deductions generally can’t drop your effective pay below the federal minimum wage. The Fair Labor Standards Act requires wages to be paid “free and clear,” so an employer can’t use deductions to claw back pay in a way that benefits the employer or breaches the minimum.13eCFR. 29 CFR 531.35 – Wage Payments Free and Clear Employers also can’t profit directly or indirectly from voluntary deductions forwarded to third parties like insurers or charities.14eCFR. 29 CFR 531.40 – Payments to Employee’s Assignee Many states add their own floor on top of that, sometimes tied to a higher state minimum. If you earn near minimum wage and have several voluntary deductions stacked up, check the math on your pay stub.