401(k) plan

Editorial approval scope: The team checked current source fidelity, scope boundaries, dates, arithmetic, reader usefulness, practical workflow, and general-information limitations.

A 401(k) is governed by a written plan

The Department of Labor retirement page identifies 401(k) plans as employer retirement plans and explains that ERISA covers most private-sector pension plans. The written plan and adoption agreement define eligibility, entry, contributions, vesting, distributions, loans, and other available features within governing law.

A provider's sales page or payroll setting is not the plan. Keep the executed plan document, amendments, summary plan description, participant notices, service agreements, investment policy materials, and current contacts together.

Choose design features intentionally

Common choices include traditional or Roth elective deferrals, employer match, nonelective contributions, safe-harbor design, automatic enrollment, vesting, loans, hardship distributions, and eligibility rules. Each feature affects administration, cost, communications, and testing.

Model employees with varied schedules, hire dates, ages, compensation, and turnover. ABA practices often have hourly staff, supervisors, administrative employees, owners, and workers across states. A design that looks simple for one group can create unexpected entry or contribution outcomes elsewhere.

Payroll must follow elections and limits

The payroll system needs the effective election, source type, compensation definition, plan-year limit, catch-up status, employer formula, and funding route. Deferrals withheld from pay must reach the plan within the applicable timing rules. A payroll export marked complete does not prove plan deposit.

Reconcile each payroll from gross compensation through eligible compensation, employee deferral, employer contribution, remittance, plan receipt, and general ledger. Track rejected files and returned money to final resolution.

Annual contribution limits change

The IRS contribution-limits page states that the 2026 elective-deferral limit for traditional and safe-harbor 401(k) plans is $24,500. The ordinary age-50 catch-up is $8,000, and a higher $11,250 catch-up applies at ages 60 through 63 when the requirements are met.

The 2026 annual-additions limit is generally the lesser of 100% of compensation or $72,000, with catch-up treatment described separately by the IRS. These figures are time-sensitive. Plan terms can impose lower limits, and nondiscrimination or other rules can reduce a participant's available amount.

Fiduciary responsibility stays with named roles

Hiring a recordkeeper, payroll vendor, investment adviser, or third-party administrator does not transfer every duty. The DOL's fiduciary guide explains prudence, loyalty, plan-document compliance, fee reasonableness, diversification, and prohibited-transaction concerns.

Name the plan sponsor, administrator, trustee, fiduciaries, payroll owner, contribution approver, and escalation route. Review service providers and fees at a documented cadence. Keep decisions and monitoring evidence.

Eligibility and notices need a due cohort

Track each worker's employment date, age when applicable, service, classification, entry date, election, notice due dates, beneficiary data, and status. Apply the plan's definition rather than a manager's expectation.

Provide required materials through a valid delivery method and preserve evidence. A portal upload without delivery evidence may leave the task unresolved. Accessible formats and language support should be built into enrollment.

A fictional launch register

Cedar Gate ABA defines 12 launch gates covering signed documents, eligibility coding, payroll testing, remittance, investments, notices, fiduciary appointments, fees, cybersecurity, correction routing, filing ownership, and employee support. Ten are ready. Payroll-to-trust timing and one vendor-access role remain held.

Launch readiness is 10 of 12 gates, or 83.3%. Both held gates stay in the denominator. The practice delays the first deduction until the responsible specialists clear them. This ratio measures implementation evidence, not plan quality or compliance.

Testing and corrections belong in operations

Traditional plans may face nondiscrimination testing, while safe-harbor plans have their own design and notice conditions. Plans can also require top-heavy, coverage, contribution, and annual reporting work. Identify the test, data owner, due date, reviewer, and correction route.

Errors can involve missed deferrals, wrong compensation, late deposits, excluded employees, excess contributions, or incorrect matches. Preserve source data and use the current IRS or DOL correction program with qualified advice. Avoid inventing a payroll-only fix that leaves the plan record inconsistent.

Participant support and security matter

Employees need a usable path for enrollment, beneficiary changes, rollover questions, distributions, loans when offered, and complaints. Explain which questions belong to payroll, the plan administrator, recordkeeper, investment adviser, or tax professional. Avoid giving individualized investment advice from an operations inbox.

Retirement accounts contain identity, beneficiary, balance, and bank data. Apply role-based access, multifactor authentication, secure delivery, vendor monitoring, and prompt access removal. Reconcile participant complaints about missing contributions against payroll and trust records rather than closing them from a vendor screenshot.

Before each plan year and first payroll, approve the signed plan terms, eligibility population, compensation definition, limits, match formula, catch-up handling, payroll codes, deposit route, notices, and vendor access. Run employee-level test cases and retain expected results so production deductions are released against evidence rather than configuration confidence.