What are payroll deductions?

Every paycheck tells a story. Gross pay goes in at the top, net pay comes out at the bottom, and in between sits a list of deductions that determines what employees take home — and what employers owe.

Payroll deductions are amounts subtracted from an employee's gross pay to cover benefits, taxes, or other withholdings before delivering net pay. They fall into two categories: pre-tax and post-tax. Getting the classification right determines your compliance exposure, your employer tax liability, and whether your workforce gets the full benefit of the programs you offer.

Misclassify a deduction and you face payroll errors, IRS scrutiny, and potentially costly corrections. The IRS assessed $84.1 billion in civil penalties in fiscal year 2024, with the majority tied to employment tax violations.

With 2026 bringing updated contribution limits, new W-2 reporting codes, and a significant rule change for 401(k) catch-up contributions, there is no better time to make your deduction management airtight.

This guide covers what HR and finance leaders need to know: how each deduction type works, how they affect taxes and take-home pay, what's changed in 2026, and how to build controls that keep your US payroll compliant.

What are pre-tax deductions?

Pre-tax deductions are amounts subtracted from gross wages before calculating payroll taxes, reducing taxable wages and increasing take-home pay.

The specific taxes affected depend on the deduction type. Section 125 plan elections — including health insurance premiums, FSAs, HSAs, and dependent care FSAs — reduce wages subject to both federal income tax and FICA (Social Security and Medicare).

Traditional 401(k) contributions reduce federal income tax withholding, but the full gross wage still applies for Social Security and Medicare. For every qualifying Section 125 dollar, the employer's FICA liability drops by 7.65%.

Common pre-tax deduction types include:

• Health insurance premiums (employer-sponsored)
• Health Flexible Spending Accounts (FSAs)
• Health Savings Accounts (HSAs)
• Traditional 401(k) and other qualified retirement plan contributions
• Commuter benefits (transit and parking)
• Dependent care FSAs
• Section 125 cafeteria plan elections

What are post-tax deductions?

Post-tax deductions are amounts withheld from an employee's pay after payroll taxes are calculated, reducing net pay but not lowering taxable income.

Because taxes are calculated first, post-tax deductions do not reduce the employee's tax burden or the employer's FICA liability. They reduce the final amount that reaches the employee's account.

Common post-tax deduction types include:

• Wage garnishments (child support, alimony, student loans, back taxes)
• Union dues
• Charitable contributions
• Roth 401(k) contributions (post-tax contributions; qualified withdrawals are tax-free)
• Life insurance premiums above the IRS exclusion threshold
• Non-qualified benefit premiums

Getting the classification right matters in both directions. Treating a post-tax item as pre-tax undertaxes employees and creates audit exposure. Treating a pre-tax item as post-tax overtaxes them and creates a refund liability.

Key differences between pre-tax and post-tax deductions

Misclassification produces incorrect W-2s, IRS penalties, and employee disputes. The IRS FY2024 Data Book shows the IRS assessed more than 1.17 million penalties for federal tax deposit failures in FY2024, totalling nearly $19 billion. Systematic controls are the only reliable way to prevent your organization from contributing to that total.

Common types of pre-tax deductions

Here are the most common pre-tax deduction types for US payroll, with 2026 contribution limits.

Health FSA

A Health Flexible Spending Account lets employees set aside pre-tax dollars for qualified medical expenses. The 2026 employee contribution limit is $3,400 (up from $3,300 in 2025). The maximum carryover for re-enrolled employees is $680. Funds are typically subject to a use-it-or-lose-it rule, though some employers offer a grace period or carryover allowance under their plan terms.

Dependent care FSA

A Dependent Care FSA covers eligible dependent care expenses such as childcare, preschool, and elder care. Contributions are pre-tax and reduce wages subject to both income tax and FICA. Dependent care FSA funds do not carry over; unused balances are forfeited, with a 90-day runout period for submitting claims. Confirm the current IRS annual limit with your benefits administrator before open enrollment.

Health Savings Account (HSA)

Available only to employees enrolled in a qualifying High Deductible Health Plan (HDHP). Contributions from the employee, employer, or both are pre-tax, and unused funds roll over indefinitely with no expiry. The 2026 limits are $4,400 for individual coverage and $8,750 for family coverage (up from $4,300 and $8,550 in 2025). Employees can adjust their HSA contributions at any time during the year, giving them more flexibility than an FSA election.

Traditional 401(k) and retirement deferrals

Traditional 401(k) contributions reduce federal income tax withholding but are still subject to Social Security and Medicare taxes. The full gross wage applies for FICA purposes. The 2026 elective deferral limit is $24,500, and the Roth catch-up wage threshold increased to $150,000 for 2026.

Employees aged 50 and over who earned more than $150,000 in Social Security wages in 2025 must make all 2026 catch-up contributions on a Roth (after-tax) basis. Employees earning below that threshold can still make pre-tax catch-up contributions.

Commuter benefits

Employer-sponsored transit and parking programs are exempt from federal income and FICA taxes up to the IRS monthly limit. The 2026 monthly transit benefit exclusion is $340. Self-employed individuals, independent contractors, partners, and 2% S-corporation shareholders are not eligible.

Section 125 cafeteria plans

Section 125 plans allow employees to choose from a menu of pre-tax benefits. Premium-only plans, FSAs, and HSAs typically operate under Section 125. These plans must be formally documented. An oral or informal arrangement does not qualify, and they are subject to annual non-discrimination testing.

Common types of post-tax deductions

Post-tax deductions require the same operational discipline as pre-tax ones, even though they carry no tax advantage.

Wage garnishments

Court- or agency-ordered deductions, most commonly for child support, alimony, student loans, or tax debts. Employers must comply precisely with garnishment order terms. Sequencing errors and missed remittances create direct legal liability.

Union dues

Withheld post-tax for employees covered by a collective bargaining agreement. Amounts and frequency are set by the union contract.

Roth 401(k) contributions

Roth contributions use after-tax dollars. The same $24,500 annual limit applies as for traditional contributions, but qualified distributions are tax-free. Starting January 1, 2026, employees aged 50 and over who earned more than $150,000 in Social Security wages in the prior year must make all catch-up contributions on a Roth basis.

Charitable contributions

Voluntary donations withheld from pay carry no payroll-level tax benefit, though employees may deduct them on personal tax returns.

Non-qualified insurance premiums

Life insurance coverage above the IRS-excluded $50,000 threshold for employer-paid group term life is a taxable benefit. Imputed income for excess coverage must appear on the employee's W-2.

Tax implications for employers and employees

Understanding how deduction types interact with payroll taxes is foundational to accurate processing and clear employee communication.

How the math works for pre-tax deductions:

• Gross pay – pre-tax deductions = taxable wages → taxes calculated on taxable wages → taxable wages – taxes = net pay (before post-tax deductions)

How the math works for post-tax deductions:

• Gross pay – taxes = after-tax pay → after-tax pay – post-tax deductions = net pay

The key FICA distinction: Section 125 plan elections — health insurance, FSAs, HSAs, and dependent care FSAs — reduce wages subject to both federal income tax and Social Security and Medicare taxes. Traditional 401(k) contributions reduce only federal income tax withholding. The full gross wage still counts for FICA when an employee makes a 401(k) election.

This distinction is relevant for employer cost modeling, benefit plan design, and the communications your team sends during open enrollment. Post-tax deductions have no effect on any of these calculations, because all tax withholding is assessed before they are applied.

Impact on take-home pay

Here's a concrete side-by-side example.

Scenario: An employee earns $60,000 annually ($5,000 monthly gross). They contribute $400 per month to a traditional 401(k) and pay $200 per month in union dues.

The 401(k) contribution saves this employee roughly $88 in federal income tax each month. A health FSA or HSA election would reduce FICA as well, because those are Section 125 plan elections. A traditional 401(k) does not. The union dues reduce neither federal income tax nor FICA.

Showing employees this comparison at open enrollment gives them the information to make better-informed benefit decisions.

Employer payroll tax considerations

Every qualifying Section 125 dollar reduces your FICA liability by 7.65%. For an organization with 200 employees each contributing $3,000 annually to a health FSA, that's a $45,900 reduction in employer FICA before accounting for HSA elections, health insurance premium cost-sharing, or dependent care FSA participation.

Pre-tax benefits also require proactive monitoring:

• Contribution caps: Exceeding IRS annual limits creates a refund obligation and triggers audit risk. Over-contributions must be corrected before the tax year closes
• Plan document compliance: Section 125 plans must be in writing, formally adopted, and operated according to their terms
• Non-discrimination testing: FSAs, 401(k) plans, and Section 125 plans face annual non-discrimination tests to confirm benefits do not disproportionately favor highly compensated employees

For post-tax deductions, the primary risk is sequencing accuracy, particularly for garnishments, which carry strict legal obligations on timing, amounts, and remittance.

2026 compliance requirements

For organizations managing payroll across multiple states or with distributed and remote teams, the compliance surface is wider than for single-state employers.

System readiness priorities before January payroll:

• Update deduction tables and contribution limits for all benefit plan types
• Configure new IRS W-2 reporting codes for qualified tips and overtime pay, which debut on 2026 forms
• Apply the mandatory Roth catch-up rule: the wage threshold is $150,000 for 2026, up from $145,000 in 2025
• Verify electronic filing readiness. E-filing is mandatory for most applicable large employers
• Confirm location-based withholding logic for employees working across state lines

Remote workforce complexity: Withholding is based on where the employee performs work. State rules on deduction treatment and income tax withholding vary considerably. Several states have enacted mandatory leave or benefit deductions that interact with federal pre-tax and post-tax classifications in ways that differ by jurisdiction.

Audit trails: Every deduction change — from a benefit election, a correction, or a regulatory update — needs documented authorization and a timestamped record. This is the foundation of an auditable US payroll process.

Legislative changes affecting deductions

Several limits and reporting rules changed for 2026 that directly affect US payroll deduction management.

Mandatory Roth catch-up contributions: From January 1, 2026, employees aged 50 and over who earned more than $150,000 in Social Security wages in the prior year must make all 401(k) catch-up contributions on a Roth (after-tax) basis. Note: the threshold increased from $145,000 (2025) to $150,000 (2026).

New W-2 reporting codes: The IRS introduced new codes for qualified tips and overtime pay on 2026 W-2 forms. Payroll platforms need configuration updates to generate correct year-end forms.

1099-NEC reporting threshold: Now $2,000, which affects organizations that pay contractors alongside payroll employees.

IRS reporting and documentation

Accurate W-2 reporting is the year-end output of everything your deduction management produces across all 12 months. Errors at year-end almost always trace back to misclassification, missed limit updates, or inadequate year-to-date tracking earlier in the cycle.

What belongs on W-2s:

• Box 12 codes cover most pre-tax benefit contributions (Code W for HSA employer contributions, Code D for traditional 401(k) deferrals)
• Imputed income from post-tax benefits — group term life insurance above $50,000 — must appear in Box 12 or Box 1
• New 2026 codes for qualified tips and overtime now apply

Documentation retention: Keep payroll records for five to seven years. This includes benefit elections, change logs, authorization records, and garnishment orders.

E-filing: Electronic filing is mandatory for most applicable large employers filing 10 or more information returns.

A practical year-end preparation checklist:

• Confirm all deduction elections match authorized documentation
• Reconcile year-to-date totals against IRS annual limits for FSAs, HSAs, and 401(k) plans
• Confirm the mandatory Roth catch-up rule is applied at the employee level using the updated $150,000 threshold
• Review W-2 Box 12 codes across all benefit types
• Verify imputed income calculations for non-qualified benefits
• Confirm e-file enrollment and test your transmission

Managing deductions across multiple states

Deduction management for a workforce across multiple states requires more than a single federal rulebook. State rules differ from federal treatment in ways that affect deduction classification, withholding obligations, and benefit plan design.

Some states do not recognize Section 125 pre-tax status for state income tax purposes. A deduction that reduces federal taxable wages may still be taxable at the state level. California is the clearest example: HSA contributions are not exempt from California state income tax, even though they are fully exempt at the federal level under Section 223.

Work location drives withholding

For distributed and remote teams, withholding applies based on where the employee performs work. Employees who work across state lines, even temporarily, can create multi-state withholding obligations that add deduction complexity.

State-mandated benefit deductions

Several states require payroll deductions for paid family leave, state disability insurance, and long-term care programs. States with active state-level withholding programs beyond federal requirements include:

• California
• New York
• Washington
• Oregon
• Connecticut
• Colorado
• Massachusetts
• New Jersey
• Rhode Island
• Hawaii

These carry their own pre-tax and post-tax classifications and interact with federal benefit calculations in ways that vary by state. Organizations expanding into new states should audit their deduction configuration at the point of expansion.

Best practices for managing payroll deductions

Build a deduction inventory

Map every deduction type your organization administers. Document whether it's pre-tax or post-tax, the applicable federal and state tax treatment, the annual limit and how your system enforces it, the authorization workflow for elections and changes, and the W-2 reporting code. Review and update this inventory before every open enrollment and at the start of each calendar year.

Configure systems before the year begins

Update your payroll platform with current contribution limits, new withholding tables, and any new IRS or state reporting requirements before the first run of each new year. For 2026, this includes the updated FSA limit of $3,400, HSA limits of $4,400 (individual) and $8,750 (family), the $24,500 401(k) deferral limit, the mandatory Roth catch-up threshold of $150,000, and new W-2 codes.

Automate year-to-date tracking

Year-to-date tracking requires system-level cap enforcement. Over-contributions to FSAs, HSAs, and 401(k) plans are a direct path to correction filings and penalty exposure. Configure your system to flag when a worker approaches their annual limit.

Run pre-payroll reviews before every run

Catching a misclassified deduction before payroll processes costs nothing to fix. Finding it afterward requires corrections, potential IRS filings, and employee communications. Make the pre-run review a standard step in every payroll cycle.

Standardize authorization workflows

Every deduction election or change should follow a defined workflow: employee submits, HR or manager reviews, payroll approves. Every step should be timestamped and retained. This documentation is what your team needs when a worker disputes their deductions or a regulator requests records.

Communicate deduction details to employees at open enrollment

Provide employees with a clear, plain-language explanation of how pre-tax and post-tax elections affect their take-home pay, using concrete examples tied to your benefit offerings. Give access to pay stubs before payroll finalizes so employees can flag issues in advance.

How Deel Payroll handles deduction management

Accurate deduction management requires a payroll system that applies the right rules automatically, keeps current with regulatory changes without manual intervention, and gives your team full visibility before a run processes.

Deel Payroll is built on owned infrastructure. There are no third-party processors between your payroll data and the calculation engine, which means continuous compliance updates to contribution limits, withholding tables, and reporting requirements apply across your payroll without waiting on a vendor.

Watch the video below to see how Deel's built-in AI helps you stay accurate and compliant:

For US payroll, Deel Payroll (US) supports:

• Automated deduction classification and correct tax treatment by deduction type
• Real-time year-to-date contribution tracking to prevent over-contributions
• Multi-state withholding logic for distributed and remote teams
• Payroll-connected benefits administration to sync elections directly into the payroll run
• Continuous compliance updates applied automatically as federal and state rules change

Self-serve or managed, your team chooses how much to operate directly and how much to delegate. Either way, you have a single system of record for payroll, benefits, and compliance data, with full audit trails built in.

Ready to see it in action? Book a Deel Payroll demo.