401K Audit Outsourcing for CPA & Accounting Firms – Your Guide to EBP Audits

Employee-benefit-plan audits are a capacity trap: they're specialized (ERISA, DOL, SAS 136), deadline-bound (Form 5500), and clustered in the same months as everything else. Outsourcing 401(k) audit support lets your firm take on more plan audits by moving the labor-intensive workpaper preparation to a trained team — while your licensed auditors keep the judgment, the review, and the opinion.

This guide covers when an audit is required, what's prepared, full vs. limited scope, and the deadlines.

When does a 401(k) plan need an audit?

A plan generally needs an independent audit if it has 100+ eligible participants at the start of the plan year (a "large plan filer"). Plans with 80–120 participants may continue filing as a small plan (no audit) under the 80-120 rule if they did so the prior year (DOL/IRS Form 5500).

What the outsourced team prepares

Workpapers for every audit area, with your auditors retaining responsibility: - Participant data testing (eligibility, deferral %, employer match, vesting) - Contribution testing and distribution/loan testing (eligibility, withholding, RMDs, 1099-R; loan terms vs. plan limits) - Investment valuation testing (Level 1/2/3 under ASC 820; reconciliation to the trust report) - Prohibited-transaction testing - ASC 960 plan financial statements (net assets available for benefits; changes) + Form 5500 schedules

Full-scope vs. limited-scope

A full-scope audit tests all plan investments. A limited-scope audit relies on a qualified institution's certification of investment information — narrowing the work to participant data, contributions, distributions, and loans. The team prepares workpapers for either.

Standards & responsibility

Work follows SAS No. 136 (ERISA plan audits), DOL regulations, and the AICPA EBP Audit & Accounting Guide. You sign the opinion; the offshore team prepares the workpapers — your firm assesses risk, reviews, and concludes.

Deadlines

Form 5500 is due 7 months after plan year-end (July 31 for calendar-year plans); a Form 5558 extension adds 2.5 months (to October 15). The team tracks these per plan so workpapers reach the partner with review time to spare.

Why outsourcing it works

Seasonal EBP capacity without seasonal hiring, at up to 70–75% less than in-house staff for the same preparatory work — letting your firm take on more plan audits with the team you have.

How Acculink CPA fits

Acculink is an India-based (Ahmedabad) team working exclusively with U.S. CPA and accounting firms — 300+ professionals trained in EBP audit workflows, under a two-tier review. ISO 27001:2013 certified, SOC 2 Type II–aligned, GDPR compliant, with IRS §7216 / AICPA / FTC compliance and a zero-breach record over 5+ years — participant PII (SSNs, balances) handled on encrypted systems, NDAs signed, no local storage. 40-hour free trial, no lock-in. Book a free call.

Frequently asked questions

When is a 401(k) plan audit required?

Generally when the plan has 100+ eligible participants at the start of the plan year; the 80-120 rule lets some 80–120-participant plans keep filing as a small plan (no audit) if they did so the prior year.

What does the outsourced team prepare?

Workpapers for participant-data, contribution, distribution/loan, investment-valuation, and prohibited-transaction testing, plus ASC 960 plan financial statements and Form 5500 schedules.

What's the difference between full-scope and limited-scope?

Full-scope tests all plan investments; limited-scope relies on a qualified institution's certification, narrowing the audit to participant data, contributions, distributions, and loans.

What standards are followed?

SAS No. 136, DOL regulations, and the AICPA EBP Audit & Accounting Guide — with your firm retaining the audit opinion.

What's the Form 5500 deadline?

Seven months after plan year-end (July 31 for calendar-year plans); a Form 5558 extension moves it to October 15.

Is participant data secure?

Yes — ISO 27001:2013 certified and SOC 2 Type II–aligned; participant PII is handled on encrypted systems in monitored facilities, with NDAs and no local storage.