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Late Deposits: The Most Common (and Costly) 401k Error

by | Apr 29, 2026

As 401(k) audits ramp up across the country, plan sponsors have a critical opportunity to address common compliance issues before they turn into audit findings. Based on hundreds of audits performed by PriceKubecka, one issue consistently rises to the top.👉Late 401(k) deposits.

What Is a Late 401(k) Deposit?

When employees defer part of their paycheck into a 401(k), those funds must be deposited into the plan as soon as administratively possible.

Yes, there’s a rule about the 15th business day of the following month—but here’s what most plan sponsors miss: That’s NOT a safe harbor. It’s the absolute maximum deadline.

The real standard is: Deposit contributions as soon as you reasonably can.

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Why This Trips Up Plan Sponsors

Let’s say you typically deposit contributions 3 days after payroll. That becomes your benchmark.

So if the next deposit happens 10 days after payroll… That’s a late deposit—even if it’s before the 15th business day.

This is where most companies get flagged in audits.

What Happens If You Have Late Deposits?

If your auditor identifies late deposits, you’re required to:

  1. Calculate Lost Earnings – Determine how much participants missed out on because their money wasn’t invested.
  1. Make Participants Whole – You must fund the difference. This is your correction (penalty).
  1. Report It – Late deposits are disclosed in:

👉 And yes, this gets the attention of the Department of Labor (DOL).

When Late Deposits Become a Bigger Problem

Occasional delays happen. But repeated late deposits? That’s a pattern—and a red flag. Unchecked, this can:

  • Trigger DOL scrutiny
  • Lead to expanded investigations
  • Create ongoing compliance risk

How to Fix Late Deposits (For Good)

The solution is simple but it requires discipline.

1. Make 401(k) deposits part of payroll

Treat them like payroll taxes. Same day. No exceptions.

2. Establish a consistent timeline

Whatever your “as soon as possible” timeline is—stick to it.

3. Build redundancy into the process

  • Train a backup processor
  • Ensure coverage during PTO or turnover

4. Document everything

If a delay happens, it’s vital to record why it occured and what corrective action was taken.

5. Align systems and providers

Work with your payroll provider and recordkeeper to:

  • Define your earliest deposit timing
  • Ensure systems support it

Bottom Line

Late deposits aren’t complicated—but they are high-risk and highly visible.

The good news? They’re also one of the easiest audit findings to eliminate entirely.

Work With a 401(k) Audit Specialist

If late deposits showed up in your audit—or you want to make sure they don’t next year—PriceKubecka can help. We specialize in streamlined, flat-fee 401(k) audits that:

👉 Let’s make next year’s audit your easiest one yet.

Frequently Asked Questions

What is considered a late 401(k) deposit?

A late 401(k) deposit occurs when employee deferrals are not deposited into the plan as soon as administratively possible, even if they are deposited before the 15th business day of the following month.

Is the 15th business day rule a safe harbor for 401(k) deposits?

No. The 15th business day is the maximum deadline, not a safe harbor. Employers must deposit contributions as quickly as they reasonably can, often within a few days of payroll.

How do you correct late 401(k) deposits?

To correct late deposits, plan sponsors must:

  • Calculate lost earnings for participants
  • Deposit those earnings into participant accounts
  • Report the issue on Form 5500 and audit disclosures
Can late 401(k) deposits trigger a DOL audit?

Yes. Repeated or significant late deposits can attract attention from the Department of Labor (DOL) and may lead to further investigation or penalties.

How can employers prevent late 401(k) deposits?

Employers can prevent late deposits by:

  • Depositing contributions at the same time as payroll
  • Creating a consistent, documented process
  • Training backup personnel
  • Coordinating with payroll providers and recordkeepers
Does a Fiscal-Year 401(k) Plan Still Need an Audit?

Potentially, yes.

Operating on a fiscal year does not eliminate or change the basic requirement for an independent employee benefit plan audit. Whether a defined contribution plan requires an audit generally depends on its Form 5500 filing status and the applicable participant-count rules—not whether its plan year ends December 31.

For defined contribution plans, the relevant participant count now focuses on participants and beneficiaries who have account balances at the beginning of the plan year, rather than everyone merely eligible to participate.

So an off-cycle plan sponsor should answer two separate questions:

Do we have an audit requirement?

And, if so:

When must that audit be completed so our Form 5500 can be filed on time?

Those are related questions, but they aren’t the same question.

When Should a Fiscal-Year 401(k) Audit Start?

The Form 5500 deadline should be the end of your audit timeline—not the beginning of it. The safest approach is to work backward from your actual filing deadline and establish the audit schedule well in advance.

If an independent audit is required, the auditor’s report generally accompanies the Form 5500 filing. That means the audit needs to be substantially complete before your filing deadline arrives.

There isn’t one audit-start date that works for every plan. The amount of time needed depends on factors such as plan size, the availability of records, the complexity of the plan and whether testing identifies issues requiring follow-up.

A practical timeline should allow time for:

Data collection: Your team may need to gather census information, payroll data, contribution records, recordkeeper reports, participant files and plan documents.

Audit testing: Your auditor will perform required procedures and may select participants or transactions for additional documentation.

Follow-up questions: Missing information and discrepancies often require responses from HR, payroll, the recordkeeper, TPA or other providers.

Resolving exceptions: Eligibility errors, contribution discrepancies, participant loans, distributions, compensation issues and other findings can require additional investigation.

Final review and issuance: The audit team still needs time to complete its review and issue the auditor’s report before the Form 5500 is finalized.

Example: A 401(k) Plan With a March 31 Year-End

Suppose your plan year ends March 31.

Your normal Form 5500 deadline is generally October 31.

With a timely Form 5558 extension, the deadline can generally be extended to January 15.

That does not mean January should become your target date for beginning the audit.

Instead, the plan sponsor and auditor should establish a timeline that leaves enough time before the applicable deadline to obtain records, complete testing and address any unexpected issues.

In other words:

March 31 plan year-end → October 31 normal deadline → January 15 extended deadline

Your audit calendar should be built backward from whichever filing deadline applies.

Example: A 401(k) Plan With a June 30 Year-End

A June 30 plan operates on a very different schedule.

Its Form 5500 would generally be due January 31 of the following year.

With a timely Form 5558 extension, the deadline would generally move to April 15.

For that employer, traditional summer 401(k) “audit season” may be largely irrelevant. Its audit preparation and testing may instead take place during the fall and winter.

That is why a plan with a non-calendar-year end should work with an auditor that maintains employee benefit plan audit capabilities throughout the year.

What Can Delay an Off-Cycle 401(k) Audit?

Having a different deadline doesn’t protect a plan from the same issues that slow down calendar-year audits.

Some common audit roadblocks include:

  • Missing or inaccurate census information
  • Eligibility and plan entry-date errors
  • Incorrect employer contribution or match calculations
  • Incorrect application of the plan’s compensation definition
  • Late participant contributions
  • Participant loan problems
  • Vesting or forfeiture discrepancies
  • Distribution documentation issues
  • Differences between payroll and recordkeeper data
  • Delays obtaining information from outside service providers

One of the advantages of starting early is having time to resolve those issues before they become filing-deadline problems.

What If Your Fiscal-Year Form 5500 Deadline Falls on a Weekend or Holiday?

There is an important exception to the dates in the chart.

If a Form 5500 filing deadline falls on a Saturday, Sunday or federal holiday, the filing can generally be made on the next day that is not a Saturday, Sunday or federal holiday. U.S. Department of Labor

That means sponsors should verify the precise deadline for the applicable filing year rather than relying solely on a recurring calendar.

The month-by-month chart is best used as a planning guide.

What About Short Plan Years?

A short plan year can occur when, for example, a plan changes its plan-year end or terminates and completes the distribution of plan assets.

The general Form 5500 timing rule still applies: the filing is generally due by the last day of the seventh calendar month after the short plan year ends, subject to an authorized extension. U.S. Department of Labor

Short plan years can introduce additional reporting and audit considerations, so sponsors should coordinate the filing timeline with their TPA, auditor and other advisors rather than assuming the normal annual schedule applies.

Don’t Build Your Audit Around October 15 If October 15 Isn’t Your Deadline

October 15 gets enormous attention in the 401(k) industry because it is the extended Form 5500 deadline for many calendar-year plans.

But it’s only one deadline.

For a non-calendar-year plan, your filing date could fall in January, April, June, November—or virtually any other month.

Your audit calendar should therefore begin with three questions:

When does our 401(k) plan year end?

When is our Form 5500 due?

When does the audit need to begin to comfortably meet that deadline?

Once those dates are established, your organization can build a recurring compliance calendar around its own plan rather than someone else’s audit season.

Looking for a 401(k) Auditor for a Fiscal-Year Plan?

PriceKubecka performs employee benefit plan audits throughout the year for both calendar-year and non-calendar-year 401(k) plans.

Our employee benefit plan specialists perform more than 400 EBP audits annually, including 401(k), 403(b) and ESOP audits. Because employee benefit plan auditing is a significant part of our audit practice, we can work with plan sponsors whose audit and Form 5500 deadlines fall throughout the year.

Whether your plan ends March 31, June 30, September 30 or another date, your audit should be built around your plan year and your deadline.

[Talk to a 401(k) Auditor]

Example: A 401(k) Plan With a March 31 Year-End

Suppose your plan year ends March 31. Your normal Form 5500 deadline is generally October 31.

With a timely Form 5558 extension, the deadline can generally be extended to January 15.

That does not mean January should become your target date for beginning the audit.

Instead, the plan sponsor and auditor should establish a timeline that leaves enough time before the applicable deadline to obtain records, complete testing and address any unexpected issues.

In other words:

March 31 plan year-end → October 31 normal deadline → January 15 extended deadline

Example: A 401(k) Plan With a June 30 Year-End

A June 30 plan operates on a very different schedule.

This plan’s Form 5500 would generally be due January 31 of the following year. With a timely Form 5558 extension, the deadline would generally move to April 15.

For that employer, traditional summer 401(k) “audit season” may be largely irrelevant. Its audit prep and testing may instead take place during the fall and winter.

That’s why a plan with a non-calendar-year end should work with an auditor that maintains EBP audit capabilities throughout the year.

In other words:

June 30 plan year-end → January 31 normal deadline → April 15 extended deadline

What Can Delay an Off-Cycle 401(k) Audit?

Having a different deadline doesn’t protect a plan from the same issues that slow down calendar-year audits. Some common audit roadblocks include:

  • Missing or inaccurate census information
  • Eligibility and plan entry-date errors
  • Incorrect employer contribution or match calculations
  • Incorrect application of the plan’s compensation definition
  • Late participant contributions
  • Participant loan problems
  • Vesting or forfeiture discrepancies
  • Distribution documentation issues
  • Differences between payroll and recordkeeper data
  • Delays obtaining information from outside service providers

One of the advantages of starting early is having time to resolve those issues before they become filing-deadline problems.

What If Your Fiscal-Year Form 5500 Deadline Falls on a Weekend or Holiday?

There is an important exception to the dates in the chart. If a Form 5500 filing deadline falls on a Saturday, Sunday or federal holiday, the filing can generally be made on the next day that is not a Saturday, Sunday, or federal holiday. 

That means sponsors should verify the precise deadline for the applicable filing year rather than relying solely on a recurring calendar. The month-by-month chart is best used as a planning guide.

What About Short Plan Years?

A short plan year can occur when, for example, a plan changes its plan-year end or terminates and completes the distribution of plan assets.

In this case, the general Form 5500 timing rule still applies: the filing is generally due by the last day of the seventh calendar month after the short plan year ends, subject to an authorized extension. 

Short plan years can introduce additional reporting and audit considerations, so sponsors should coordinate the filing timeline with their TPA, auditor, and other advisors rather than assuming the normal annual schedule applies.

Don’t Build Your Audit Around October 15 if it isn’t Your Deadline

October 15 gets enormous attention in the 401(k) industry because it is the extended Form 5500 deadline for many calendar-year plans. But it’s only one deadline.

For a non-calendar-year plan, your filing date could fall in January, April, June, November—or virtually any other month. Your audit calendar should therefore begin with three questions:

  1. When does our 401(k) plan year end?
  2. When is our Form 5500 due?
  3. When does the audit need to begin to comfortably meet that deadline?

Once those dates are established, your organization can build a recurring compliance calendar around its own plan rather than someone else’s audit season.

Looking for a 401(k) Auditor for a Fiscal-Year Plan?

PriceKubecka performs employee benefit plan audits throughout the year for both calendar-year and non-calendar-year 401(k) plans.

Our EBP specialists perform more than 400 audits annually, including 401(k), 403(b) and ESOP audits. Because employee benefit plan auditing is a significant part of our audit practice, we can work with plan sponsors whose audit and Form 5500 deadlines fall throughout the year.

Whether your plan ends March 31, June 30, September 30, or another date, your audit should be built around your plan year and your deadline.

[Talk to a 401(k) Auditor]

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