Schedule MB: Form 5500 Filing Guide for Multiemployer Defined Benefit Plans

Who Must File Schedule MB

Schedule MB reports actuarial and minimum funding information for certain retirement plans. It primarily applies to multiemployer defined benefit plans and, in specific cases, money purchase and target
benefit plans.

Here’s a quick breakdown of who needs Schedule MB and how the filing requirements differ:

• 1

  Multiemployer Defined Benefit Plans

  A multiemployer defined benefit plan subject to the minimum funding standards under IRC §412 and ERISA §431 must file a completed Schedule MB prepared and signed by the plan's enrolled actuary.

  For these plans:

  • Schedule MB is filed with Form 5500.
  • Multiemployer plans cannot file Form 5500-SF, regardless of participant count or other small-plan characteristics.
  • The Schedule MB must be prepared and signed by an enrolled actuary.

  Key point: A multiemployer defined benefit plan files Form 5500 with Schedule MB. Form 5500-SF is not an option for this type of plan.

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• 2

  Money Purchase and Target Benefit Plans

  Schedule MB can also apply to money purchase pension plans, including target benefit plans. Unlike most defined contribution plans, these plans are subject to the minimum funding standards under IRC §412 because their required employer contributions are generally fixed and mandatory.

  Because the required contributions for these plans are generally fixed rather than discretionary, a plan may be eligible to request a waiver of the minimum funding standard when it cannot meet the required funding level.

  For these plans:

  • Only Lines 3, 9, and 10 of Schedule MB are completed.
  • An enrolled actuary's signature is not required.
  • The plan may file Schedule MB with Form 5500 or Form 5500-SF, provided it otherwise qualifies to use that form.

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• 3

  Target Benefit Plans

  A target benefit plan is a type of money purchase plan that uses actuarial calculations to set contributions toward a target retirement benefit. Unlike a defined benefit plan, the actual retirement benefit depends on the participant’s account balance and investment performance.

  For These Plans

  • Only Completes Lines 3, 9, and 10
  • Does not require an enrolled actuary’s signature
  • May file Schedule MB with Form 5500 or Form 5500-SF, if otherwise eligible

Schedule MB Exceptions to Know

• 1

  When a Multiemployer Plan Terminates

  Schedule MB remains required through the last day of the plan year in which the plan terminates. No Schedule MB is required for later years.

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• 2

  When Filing Form 5500-EZ

  Schedule MB is not filed with Form 5500-EZ, whether filed on paper or through EFAST2. Applicable funding standard account requirements still apply, and the completed schedule should be retained with plan records.

Actuary Requirements for Schedule MB

Schedule MB isn't something you complete on your own. It must be prepared and certified by an enrolled actuary, who is responsible for the plan's actuarial calculations, assumptions, funding information, and required certification.

What the Actuary Provides

• Valuation & assumptions — Actuarial valuation date, current liability calculations, mortality tables, and applicable actuarial methods.
• Funding calculations — Funding standard account, current liability, and required contribution amounts.
• Certification — Actuary's name, enrollment number, required statement, and signature.

Schedule MB Needs a Signature You Can't Skip

Except for the specific exception below, Schedule MB must be signed by the enrolled actuary. For electronic filing, an electronic reproduction of the signed Schedule MB must be attached and labeled "MB Actuary Signature".

When an Actuary's Signature Isn't Required

If the plan is a money purchase defined contribution plan, including a target benefit plan, that received a waiver of the minimum funding standard currently being amortized, Schedule MB doesn't require an enrolled actuary's signature. Lines 3, 9, and 10 must still be completed and included in the EFAST2 filing, but a signed PDF attachment isn't required in this case.

The signed PDF must be labeled “MB Actuary Signature.” Get the label wrong, and your filing can get flagged even if every number is correct.

Information Required to Complete Schedule MB

• 1

  Plan & Valuation Details

  • Plan name, sponsor name, EIN, and plan number
  • Actuarial valuation date
  • Current and actuarial value of plan assets

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• 2

  Funding & Contributions

  • Funding standard account information
  • Employer and employee contributions
  • Amortization bases, charges, and credits, where applicable
  • Withdrawal liability payments, where applicable

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• 3

  Plan Status & Funding

  • Funded percentage and applicable plan status
  • Funding Improvement or Rehabilitation Plan information, when applicable
  • Required information for plans in critical or critical and declining status

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• 4

  Actuarial & Benefit Information

  • Required actuarial calculations and assumptions
  • Expected benefit payments and other required projections
  • Other actuarial information required by Schedule MB

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• 5

  Enrolled Actuary Certification

  • Enrolled actuary's name and most recent enrollment number
  • Required certification, signature, and date
  • “MB Actuary Signature” attachment, when required

Schedule MB Filing Deadline: Extensions, Penalties & Corrections

How to Correct or Amend a Filed Schedule MB?

Errors can be corrected by amending the return directly through EFAST2, at no additional fee. For filings that are significantly late, the DOL's Delinquent Filer Voluntary Compliance Program offers a path to catch up at a reduced penalty.

Know Your Form 5500 Series Deadline

Enter your plan year-end date to find your filing deadline and see whether you may need an extension.

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Find your Deadline

Please select your plan year-end month and year.

FILING DEADLINE

April 30, 2027

For a plan year ending September 2, 2026.

You have 242 days remaining to file

E-File Now

Need more time?

File Form 5558 by your original due date to get an automatic extension of up to 2½ months.

EXTENDED DEADLINE:

July 15, 2027

Deadline passed. Form 5558 must be filed before the deadline.

Learn More About Form 5558

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Common Schedule MB Filing Mistakes

Avoid common errors and review these key requirements before submitting your Schedule MB.

Common Mistakes	Fix
Incorrect Actuary Signature Attachment	Use the exact "MB Actuary Signature" attachment label.
Using Schedule SB Instead of MB	Confirm the plan is multiemployer, not a single-employer or multiple-employer plan, before filing.
Missing Zone Status Certification	Attach the actuarial certification whenever the plan is certified as endangered, seriously endangered, critical, or critical and declining. See Required Information for what to include.
Visible Social Security Number on an Attachment	Never include one. Schedule MB and its attachments are open to public inspection, and inclusion can cause the filing to be rejected.
Over-Filing or Under-Filing the Lines	Money purchase plans on Form 5500-SF only need lines 3, 9, and 10 completed; filing the full schedule, or skipping required lines, both cause processing issues.

Schedule MB Filing Checklist

Before submitting your return, use this quick checklist to make sure your Schedule MB is complete and ready to file.

• Correct plan type identified (multiemployer or money purchase)
• Correct schedule attached (MB)
• Actuary signature obtained, if required for your plan type
• Signature PDF labeled exactly "MB Actuary Signature," if applicable
• Only the required lines completed for your filing type
• Line 4c documentation attached, if a certification was required
• Figures match between Schedule MB and your main Form 5500 or Form 5500-SF