Controlled Group Rules for ACA Employer Counts
The 50-employee threshold for the ACA employer mandate is not measured company by company. Related employers are counted together, which surprises owners of several small businesses.
How Related Employers Are Counted
Section 4980H of the Internal Revenue Code defines the employer mandate and the aggregation rule.
The 50-Employee Test
An applicable large employer is one that averaged at least 50 full-time employees, including full-time equivalents, in the preceding year (26 U.S.C. 4980H(c)(2)). Plan the headcount analysis for the whole year, not for a single day. Because the test looks at averages, it is wise to keep monthly counts and review them with a tax adviser if the number is close. To check your own dates, use our free ACA 50-Employee calculator.
Related Employers Are One Employer
Employers treated as a single employer under Internal Revenue Code section 414(b), (c), (m) or (o) are counted together, and predecessors are included. The rules can reach entities that look separate on paper, such as companies with common owners. Employers that have grown by acquisition should ask counsel or a tax adviser how the rules apply.
What Those Sections Mean
Section 414(b) and (c) reach corporations and trades or businesses under common control, such as parent-subsidiary and brother-sister groups. Section 414(m) covers affiliated service groups, and section 414(o) lets regulations reach other arrangements used to avoid the rules. These are technical ownership and service-group rules, so the answer depends on facts that are specific to your companies. Ask counsel to review the structure rather than relying on a general reading.
Full-Time Equivalents
For employer size only, hours of employees who are not full-time are converted to full-time equivalents by dividing total hours by 120. A common method adds up hours worked by part-time staff for the month and converts them into a full-time-equivalent number. Payroll data should be reliable, and a tax adviser can check the count if it is near the threshold.
Seasonal Workers
Seasonal workers may be disregarded for the size test if the employer exceeded 50 only because of them for 120 days or fewer. The exception is narrow and depends on the facts. Keep payroll records showing the seasonal period and the headcount, and ask a tax adviser whether it applies before relying on it.
Why Owners Miss It
Each company may have 20 or 30 employees and no mandate on its own, yet together they are an applicable large employer. Owners who run several small companies often assume each is too small to be covered. If the companies are related, the combined count can change the answer, so it is worth reviewing early.
Penalty Math and Reporting for Groups
Aggregation affects both how much is owed and who files.
One 30-Employee Reduction
For penalty calculations only, the full-time count is reduced by 30. For aggregated employers, only one reduction applies, allocated among members by their full-time headcounts. The reduction is an adjustment in how a potential penalty is calculated, not in how the employer is counted. Ask a tax adviser how the reduction would be shared among members of a group.
The A Penalty
If an applicable large employer does not offer coverage to enough full-time employees and at least one receives a premium tax credit, the penalty is $3,340 per full-time employee for 2026 after the 30-employee reduction (Rev. Proc. 2025-26). See our A penalty guide.
The B Penalty
$5,010 for 2026 per full-time employee receiving subsidized Marketplace coverage, where coverage is offered but unaffordable or lacks minimum value. See our B penalty guide.
The 95% Offer Test
An applicable large employer must offer minimum essential coverage to at least 95% of its full-time employees and their dependents to avoid the A penalty. Employers should check offer rates against employees who are eligible to be counted, including those who decline coverage. Keep records of offers made, and work with a tax adviser if the rate is close to the line.
Each Member Reports
Each applicable large employer member reports its own employees on its own Forms 1094-C and 1095-C. Aggregation changes how size is counted, not who files. See our ACA reporting guide.
Response Time
Employers have at least 90 days from the IRS first letter proposing an assessment to respond (26 U.S.C. 4980H(d)(4)). Employers should read any IRS letter carefully, note the response date and contact a tax adviser right away. Do not ignore a letter, and keep copies of the forms, offers and payroll records that support your response.
What to Do If You Own More Than One Business
Start by mapping ownership.
Draw The Ownership Chart
List every entity and the owners of each. Common ownership is usually where aggregation begins. A simple chart showing each company, who owns it and what percentage they hold gives counsel what is needed to start. Update the chart whenever ownership changes, and keep it with other compliance records.
Count Across All Entities
Total the full-time and full-time equivalent employees across the group for each month of the preceding year. Use the same method for each entity and each month, and keep the worksheets. Consistency makes the count easier to explain, and a tax adviser can review the result if the total is near the threshold.
Ask Counsel About Membership
Whether a particular arrangement is a controlled group or affiliated service group is a legal determination. Have counsel confirm. Counsel can look at ownership, management and service relationships to give a clear answer. Do this before the open enrollment period, so the benefit design can reflect the result and avoid surprises.
Plan Coverage Across The Group
If the group is an applicable large employer, each member needs a compliant offer for its full-time employees. Coordinate offers, reporting and plan terms across the members so they are consistent. Ask benefits counsel or a tax adviser how the group should handle filings and who is responsible for each one.
Watch Acquisitions
Buying a company can pull both employers into one count, because predecessors are included in the aggregation. Include a review of headcount and ownership in every acquisition checklist, and bring in counsel early. Be careful about the date a deal closes, because it can affect which year’s count matters.
Calendar The Reporting
Each member’s filing is due on the usual dates. See the compliance calendar.
Questions We Get About Controlled Groups
Do my separate companies count together for the ACA?
If they are treated as a single employer under Internal Revenue Code 414(b), (c), (m) or (o), yes. Common ownership is the usual trigger.
What is the employee threshold?
An average of at least 50 full-time employees, including full-time equivalents, in the preceding calendar year.
Is the 30-employee reduction applied to each company?
No. For aggregated employers only one reduction applies, allocated among the members by full-time headcount.
Who files the 1095-C forms?
Each applicable large employer member files for its own employees.
Are seasonal workers counted?
They can be disregarded for the size test if the employer exceeds 50 only because of them for 120 days or fewer.
How are part-time hours counted?
For size only, total hours of non-full-time employees are divided by 120 to get full-time equivalents.
What if we buy another company?
Predecessors are included in the aggregation, so an acquisition can change your status.
Who decides if we are a controlled group?
It is a legal determination under the Internal Revenue Code. Ask your tax counsel.
Is this legal advice?
No. This page is general information, not legal advice. Rules change and facts differ, so confirm your situation with your attorney or tax advisor.
Related Guides
Related reading: ACA Employer Mandate A Penalty · ACA Employer Mandate B Penalty · Penalty Calculator · ACA Reporting Guide · Section 105(h) Guide
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Laws and rules referenced
26 U.S.C. § 414(b), (c) and (m) — Controlled group and affiliated service group aggregation.
26 C.F.R. § 54.4980H-1 — Definitions, including full-time employee, seasonal worker and how employees are counted.
This page is general information, not legal or tax advice. Rules change and facts matter, so confirm your situation with counsel or a qualified advisor.
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