Controlled Group Examples: Parent-Subsidiary, Brother-Sister, and Attribution

Controlled group examples fall into three patterns defined by Section 1563 of the Internal Revenue Code: parent-subsidiary chains built on 80% stock ownership, brother-sister groups where five or fewer individuals own overlapping stakes in multiple corporations, and combined groups that mix both. If your businesses fit any of these patterns, the IRS treats their employees as one workforce for retirement plan testing, counts them together for the ACA employer mandate, and makes them share a single Section 179 deduction limit.

The examples below walk through each type with the ownership math spelled out, then show how family and entity attribution can pull in businesses that look independent on paper.

Parent-Subsidiary Examples

A parent-subsidiary controlled group exists when one corporation owns at least 80% of the voting power or total stock value of another, with the parent directly owning 80% of at least one subsidiary and each additional corporation in the chain 80% owned by one or more corporations already in the group.¹

Single-Tier: One Parent, One Subsidiary

Company P owns 100% of Company S. The 80% threshold is exceeded, so P and S form a parent-subsidiary controlled group. Every employee of both companies counts as one workforce for federal testing purposes.

Multi-Tier Chain

Company A owns 90% of Company B, and Company B owns 85% of Company C. Because the 80% link holds at every level, all three entities form a single parent-subsidiary controlled group. It does not matter that Company A’s indirect stake in Company C works out to roughly 77% (90% × 85%). The test looks at each link in the chain independently, not the multiplied-through percentage.

Where the Chain Breaks

Company X owns 70% of Company Y, and an unrelated investor owns the other 30%. Company Y owns 95% of Company Z. Company Y and Z form a parent-subsidiary controlled group because the 80% link between them is intact. Company X is not part of that group because its 70% stake in Company Y falls short of 80%. Company X stands as a separate employer for federal testing purposes, even with significant influence over Company Y.

Brother-Sister Examples

The brother-sister test catches businesses that share common individual owners rather than flowing through a corporate chain. Two or more corporations qualify when five or fewer persons who are individuals, estates, or trusts satisfy two ownership tests at the same time:²

The same group of common owners collectively holds at least 80% of the voting power or stock value in each corporation.
Those same owners collectively hold more than 50% of each corporation, counting each owner’s stake only to the extent it is identical across all entities. You calculate this by taking the lowest percentage each owner holds in any of the corporations.

Both tests must be met using the same group of owners. For corporate tax purposes under Sections 1561 through 1563, only the 50% identical ownership test technically applies, but when Section 414(b) pulls these definitions into retirement plan territory, both the 80% and 50% tests apply.³ The examples below use both.

Both Tests Met

Owner A holds 60% of Company Alpha and 60% of Company Beta. Owner B holds 40% of Alpha and 40% of Beta. The 80% test passes because the two owners collectively hold 100% of both companies. For the 50% test, take each owner’s lowest stake across the two companies: Owner A’s lowest is 60%, Owner B’s lowest is 40%, totaling 100% identical ownership. Alpha and Beta form a brother-sister controlled group.

Failing the Identical Ownership Test

Owner C holds 90% of Company Delta and 10% of Company Gamma. Owner D holds 10% of Delta and 90% of Gamma. The 80% test passes because the two owners collectively hold 100% of both companies. But the 50% identical ownership test fails. Owner C’s lowest stake is 10%, Owner D’s lowest stake is 10%, and identical ownership totals only 20%. Delta and Gamma are not a brother-sister controlled group despite having the exact same two owners.

This is the scenario that trips people up most often. Two businesses can be entirely owned by the same individuals and still fall outside controlled group treatment if the ownership percentages are lopsided in opposite directions.

Failing the 80% Test

Six shareholders each own between 10% and 25% of two corporations. Any five of them together own more than 50% of each corporation with identical ownership exceeding 50%. But no combination of five or fewer shareholders reaches 80% in both entities. The brother-sister test fails because the 80% threshold cannot be met by five or fewer common owners.³

Combined Group Example

A combined group exists when three or more corporations are linked through both a parent-subsidiary relationship and a brother-sister relationship, with at least one corporation serving as the common parent in a parent-subsidiary chain and simultaneously being a member of a brother-sister group.²

In practice, this comes up when an individual owns a controlling interest in a parent corporation that itself has subsidiaries, and that same individual also owns a controlling interest in a separate, unrelated corporation. The parent, its subsidiaries, and the separately owned corporation all get pulled into one controlled group.

How Attribution Changes the Picture

Controlled group status depends not just on shares you hold directly but also on shares the IRS considers you to own through family members, business entities, and options. The attribution rules in Section 1563(e) are built specifically for controlled group determinations and differ from the general attribution rules in Section 318.⁴

Spouse Attribution Example

Owner E and Owner E’s spouse each directly hold 45% of Company Sigma and 45% of Company Tau, with unrelated employees holding the remaining 10% in each. Under family attribution, Owner E is treated as owning 90% of both companies. The 80% common ownership test passes easily, and identical ownership of 90% exceeds the 50% threshold. Sigma and Tau form a brother-sister controlled group, even though neither spouse individually holds a majority.

There is a narrow carve-out. Spousal attribution does not apply if you directly own no stock in the corporation, you are not a director or employee, and you do not participate in management during the tax year. When all three conditions are met, your spouse’s stock stays with your spouse for controlled group calculations.⁴

Family attribution also reaches children, grandchildren, parents, and grandparents.

Entity Attribution

Stock owned by a partnership is attributed to any partner holding at least a 5% capital or profits interest, in proportion to whichever interest is greater. Stock owned by an estate or trust is attributed to any beneficiary with an actuarial interest of 5% or more. Stock owned by a corporation is attributed to any shareholder owning 5% or more of the corporation’s value, proportionally.⁴

That 5% threshold matters. Under Section 318, used for stock redemptions and other contexts, corporate attribution kicks in at 50% ownership. Under the controlled group rules, it kicks in at 5%. Ownership flows through entities far more easily for controlled group purposes, catching arrangements that might look safe under other parts of the tax code.

Option Attribution

Anyone holding an option to acquire stock is treated as already owning those shares. This includes an option to acquire an option, or any chain of options that ultimately leads to stock acquisition. The rule prevents owners from hovering just below the 80% or 50% thresholds by holding options instead of shares.

Unincorporated Businesses: Sole Proprietorship Plus LLC

Section 1563 only covers corporations, but Section 414(c) extends controlled group treatment to any trades or businesses under common control, incorporated or not. The Treasury regulations apply the same parent-subsidiary and brother-sister frameworks to partnerships, LLCs, trusts, estates, and sole proprietorships.⁵

The thresholds are the same: 80% for controlling interest and more than 50% for effective control. For a partnership, “controlling interest” means 80% or more of the profits or capital interest. A sole proprietor inherently has 100% controlling interest, so if one person owns a sole proprietorship and at least 80% of a partnership, those businesses are under common control.⁵

Example: a professional runs a solo consulting practice and also owns 85% of a staffing LLC. Both businesses are under common control. Employees of both count together for retirement plan testing, even though the structures are completely different.

Why the Classification Matters

Once you identify a controlled group, several rules collapse the entities into a single employer.

For retirement plans, every employee across every entity counts as one workforce for nondiscrimination testing, minimum coverage, and contribution limits under Sections 401, 410, 411, 415, and 416.⁶ Adding a second entity with many rank-and-file workers who are not in the plan can cause a 401(k) to fail the ratio percentage test under Section 410(b), and bringing low-participation employees into the ADP and ACP calculations tightens the limit on what highly compensated employees can defer. Highly compensated employee status itself is determined on a controlled group basis, with compensation from all members during the lookback year counting toward the threshold.

For the Affordable Care Act, the combined full-time and full-time equivalent employee count across all entities determines whether you are an Applicable Large Employer. If the group reaches 50 or more, each entity is individually responsible for offering minimum essential coverage to its own full-time employees and files its own Forms 1094-C and 1095-C.⁷ A small subsidiary with 12 employees can owe ACA penalties because a sibling entity’s headcount pushed the group over the threshold.

For Section 179 expensing, controlled group members share one deduction limit rather than each claiming a full amount. For 2026, the maximum is $2,560,000, phasing out dollar-for-dollar when total qualifying purchases across the group exceed $4,090,000.⁸ The group allocates the deduction among its members either by agreement or by the common parent on a consolidated return, and no member can claim more than the cost of property it actually purchased and placed in service.⁹ The research credit under Section 41(f) works the same way: all qualifying expenses are aggregated, the credit is computed once, and then allocated proportionally.

If any of the examples above describe your ownership picture, run the ownership math before year-end testing rather than after. Catching a controlled group relationship on the front end is far cheaper than correcting a failed plan or missed ACA filing on the back end.

1
eCFR. 26 CFR 1.1563-1 – Definition of Controlled Group of Corporations and Component Members and Related Concepts
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GovInfo. 26 USC 1563 – Definitions and Special Rules
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Internal Revenue Service. Controlled and Affiliated Service Groups
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Office of the Law Revision Counsel. 26 USC 1563 – Definitions and Special Rules
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eCFR. 26 CFR 1.414(c)-2 – Two or More Trades or Businesses Under Common Control
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Office of the Law Revision Counsel. 26 USC 414 – Definitions and Special Rules
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Internal Revenue Service. Instructions for Forms 1094-C and 1095-C
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Internal Revenue Service. Internal Revenue Bulletin 2025-45 – Revenue Procedure 2025-32
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eCFR. 26 CFR 1.179-2 – Limitations on Amount Subject to Section 179 Election