ERISA Benefits Law Desk ReferenceERISA Benefits Tech, LLC

Part 5 · Chapter 3

401(k) and 401(m), ADP/ACP, §415, §416 Top-Heavy, and §404 Deductions

Law stated as of October 3, 2026 · Qualified Plan Testing, Eligibility, and Vesting

Scope and status

SECURE 2.0 implementation is still in motion — the catch-up final regulations (T.D. 10033) issued in 2025, mandatory automatic enrollment (§414A) and student-loan match are on proposed/notice guidance, and the annual indexed limits change yearly. Verify the limits, effective dates, and finalization status before relying on them.

Citations are to primary authority (Code §§401(k), 401(m), 402(g), 402A, 414(v), 414A, 415, 416, 401(l), 404, 4972, 4979; the comprehensive 401(k)/401(m) regulations — T.D. 9169 (2004) — at Treas. Reg. §§1.401(k)-1 to -6, 1.401(m)-1 to -5; the automatic-contribution regulations (T.D. 9447); the catch-up final regulations (T.D. 10033, 2025); and IRS guidance). Related questions are treated elsewhere: HCE/NHCE, compensation (§414(s)), §410(b) coverage, and §401(a)(4) rate-group/cross-testing in this Part's General Qualified Plan Testing (§410(b) and §401(a)(4)); controlled-group/ASG aggregation in Part 1 (Controlled Groups and Affiliated Service Groups); the EPCRS/VFCP correction procedure in Part 21 (Plan Corrections: EPCRS, VFCP, and DFVCP); and LTPT eligibility in this Part's Minimum Participation and Vesting.

Sections

Part A is shown in full. The other sections are listed by title; their text is available to subscribers.

Part A — The 401(k) CODA and Elective Deferrals

A1.CODA qualification

Part 5, ch. 3, § A1

A cash-or-deferred arrangement (CODA) is qualified only in a profit-sharing, stock-bonus, pre-ERISA money-purchase, or rural-cooperative plan (not a regular pension plan), must be in the written plan, must give employees an election between cash and a deferral, must satisfy the §401(k) distribution restrictions (deferrals not distributable before severance, age 59½, death, disability, hardship, or termination — see Part 6 (Distributions, Loans, Rollovers, and RMDs)), must provide 100% vesting of elective deferrals, and may not condition any other benefit (except matching) on whether the employee defers (the contingent benefit rule). Statute: Code §401(k); Final reg: Treas. Reg. §1.401(k)-1 (T.D. 9169).

A2.Elective deferrals and the §402(g) limit

Part 5, ch. 3, § A2

An individual's elective deferrals (pre-tax plus designated Roth) across all plans are capped by the §402(g) annual limit — $24,500 for 2026 indexed — verify — and the limit is personal to the participant (aggregated across unrelated employers). Statute: Code §402(g); Final reg: Treas. Reg. §1.402(g)-1. An excess deferral must be distributed (with allocable earnings) by April 15 of the following year, or it is taxed twice (in the year deferred and again when distributed).

A3.Designated Roth deferrals; SECURE 2.0 Roth employer contributions

Part 5, ch. 3, § A3

A plan may permit designated Roth elective deferrals (after-tax, separate accounting, qualified-distribution rules), which count toward the §402(g) limit. Statute: Code §402A; Final reg: Treas. Reg. §1.402A-1 (T.D. 9237/9324). Recent change SECURE 2.0 §604 permits a plan to allow participants to elect Roth (after-tax) treatment of employer matching and nonelective contributions (must be fully vested). Statute: Code §402A (as amended by SECURE 2.0 §604); IRS guidance: Notice 2024-2.

Part B — ADP and ACP Testing

  1. B1The ADP testSubscribers
  2. B2The ACP testSubscribers
  3. B3Correction of ADP/ACP failuresSubscribers

Part C — Safe Harbor and Automatic Enrollment

  1. C1Safe harbor 401(k)/401(m)Subscribers
  2. C2QACA (the automatic-enrollment safe harbor)Subscribers
  3. C3EACASubscribers
  4. C4Mandatory automatic enrollment — §414ASubscribers

Part D — Catch-Up Contributions (§414(v))

  1. D1Age-50 catch-up and the ages-60–63 super catch-upSubscribers
  2. D2The mandatory Roth catch-up for higher earnersSubscribers

Part E — Qualified Student Loan Payment (QSLP) Match

  1. E1Matching on student-loan paymentsSubscribers

Part F — §415(c) Annual Additions

  1. F1The annual-additions limitSubscribers
  2. F2§415 compensation and the limitation yearSubscribers

Part G — Permitted Disparity in Allocations (§401(l))

  1. G1DC permitted disparity and imputed disparitySubscribers

Part H — Top-Heavy (§416)

  1. H1The 60% determinationSubscribers
  2. H2Key employees (distinct from HCEs)Subscribers
  3. H3Top-heavy minimums and vestingSubscribers

Part I — §404 Employer Deduction Limits

  1. I1The DC deduction limit and elective deferralsSubscribers
  2. I2Combined DB/DC limit, carryover, and the §4972 excise taxSubscribers

Part J — Corrections and SECURE 2.0 Amendments (cross-references)

Part K — Pension-Linked Emergency Savings Accounts (PLESAs)

  1. K1What a PLESA is, and who may participateSubscribers
  2. K2Investment, withdrawal, and fee rulesSubscribers
  3. K3Matching contributions, and the anti-abuse rule that followsSubscribers
  4. K4Automatic enrollment and interaction with the rest of the planSubscribers

Part L — Saver's Match (§6433)

  1. L1Plan acceptance of Saver's Match contributionsSubscribers
  2. L2How an accepted Saver's Match contribution is treatedSubscribers
  3. L3Amendment, reporting, and status of the guidanceSubscribers

Worked examples

The first Part of each chapter is open to everyone. The remaining sections, with their authority and practice points, are available to subscribers and to clients of ERISA Benefits Law Group, PLLC whose engagement includes access.

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