Controlled Group Examples: Types, Attribution, and Tax Rules

Controlled group examples fall into three patterns the IRS uses to decide whether related businesses must be treated as a single employer: parent-subsidiary chains, brother-sister businesses with shared individual owners, and combined groups that mix the two. If your ownership fits any of these patterns at the 80% and 50% thresholds set out in Section 1563, every employee across every entity counts as one workforce for retirement plan testing, ACA coverage rules, and shared tax benefits like Section 179.¹

The examples below walk through each type with the numbers, then show how family and entity attribution can pull in businesses that look separate 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. The parent must directly own 80% of at least one subsidiary, and each additional corporation in the chain must be 80% owned by entities already in the group.²

Single-Tier Ownership

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.

A Chain Through Multiple Tiers

Company A owns 90% of Company B. Company B owns 85% of Company C. All three form one controlled group because the 80% link holds at every level. It does not matter that Company A’s indirect stake in Company C works out to roughly 77% when you multiply through. The test looks at each link independently, not the diluted percentage after several tiers.

Where a Chain Breaks

Company X owns 70% of Company Y. An unrelated investor holds the other 30%. Company Y owns 95% of Company Z. Y and Z form a parent-subsidiary controlled group because their 80% link is intact. Company X is not part of it, because its 70% stake in Y falls short of the threshold. X is a separate employer for federal testing purposes, even though it clearly has significant influence over 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 people (individuals, estates, or trusts) meet two tests at once:¹

The 80% common ownership test: those owners collectively hold at least 80% of the voting power or stock value in each corporation.
The 50% identical ownership test: those same owners hold more than 50% identically across the entities, counting each owner’s stake only to the extent it is present in every corporation being tested. You take the lowest percentage each owner holds in any of the corporations and total those.

For corporate tax purposes under Sections 1561 through 1563, only the 50% identical ownership test technically applies. But when Section 414(b) pulls the same definitions into retirement plan territory, both the 80% and 50% tests apply.³ Since retirement plan compliance is the setting where most business owners run into this, the examples use both.

Both Tests Met

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

Same Two Owners, Not a Controlled Group

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 (two owners, 100% of each). But the 50% identical ownership test fails badly. Owner C’s lowest stake across the two is 10%, and Owner D’s lowest is 10%, giving identical ownership of only 20%. Delta and Gamma are not a brother-sister controlled group despite having the exact same two owners in the exact same total proportions.

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

Too Many Owners to Cross 80%

Six shareholders each own between 10% and 25% of two corporations. Any five of them together own more than 50% of each with identical ownership above 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 chain and a brother-sister relationship, with at least one corporation serving as a parent in the chain and also as a member of the brother-sister group.¹

In practice, this arises when the same individual owns a controlling interest in a parent corporation that has subsidiaries, and separately owns a controlling interest in another corporation. The parent, its subsidiaries, and the separately owned corporation all get pulled into one controlled group.

How Attribution Changes the Answer

Controlled group status depends not just on shares held directly but also on shares the IRS considers owned through family members, business entities, and options. These constructive ownership rules sit in Section 1563(e) and are specifically written for controlled group determinations. They differ from the general attribution rules in Section 318 that apply elsewhere in the tax code.⁴

Family Attribution

You are generally treated as owning stock held by your spouse, children, grandchildren, parents, and grandparents. Spousal attribution has one narrow exception: it 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 those conditions are all met, your spouse’s stock stays with your spouse.

Entity Attribution at 5%

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

That 5% threshold is much lower than the 50% trigger under the general Section 318 rules used for stock redemptions. Ownership flows through entities far more easily for controlled group purposes, and it catches arrangements that might look safe under other parts of the code.

Options

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

A Spouse Example That Flips the Result

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. On the face of it, neither spouse has a majority in either company. Under family attribution, Owner E is treated as owning 90% of both. The 80% common ownership test passes easily, and identical ownership of 90% clears the 50% threshold. Sigma and Tau are a brother-sister controlled group.

Unincorporated Businesses Under Common Control

Section 1563 covers only 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, with the same 80% and 50% thresholds.⁵

For a partnership, controlling interest means holding 80% or more of the profits or capital interest. A sole proprietorship, by definition, is 100% owned by one person. So if a consultant runs a solo practice and also owns 80% of a staffing LLC, those two businesses are under common control. Both workforces count together for retirement plan testing, even though the businesses are structured very differently and file separate returns.

What Happens if Your Businesses Are a Controlled Group

Once the tests are met, Section 414(b) treats every employee across every entity as one workforce for the retirement plan rules under Sections 401, 410, 411, 415, and 416.⁶ Several other consequences follow.

Retirement Plan Testing

A 401(k) or other qualified plan must cover a fair cross-section of employees under the Section 410(b) coverage test, and its contribution patterns must pass nondiscrimination testing (the ADP and ACP tests for 401(k) plans). When a second entity with many rank-and-file workers is added to the denominator, plans that comfortably passed on their own can fail. Highly compensated employee status is also determined on a controlled group basis, with compensation aggregated across the group during the lookback year.

ACA Employer Mandate

Combined full-time and full-time equivalent employees across the whole group determine whether you are an Applicable Large Employer under the Affordable Care Act. Cross the 50-employee line and each entity is individually responsible for offering minimum essential coverage to its own full-time employees.⁷ For 2026, the penalty for failing to offer coverage to substantially all full-time employees is $3,340 per full-time employee (minus the first 30). Offering coverage that is unaffordable or does not meet minimum value costs $5,010 per employee who receives a subsidized marketplace plan.⁸ A small subsidiary with 12 employees can owe penalties because a sibling entity’s headcount pushed the group over 50.

Section 179 Deduction Is Shared, Not Duplicated

Members of a controlled group are treated as one taxpayer for Section 179 expensing. For 2026, the maximum deduction is $2,560,000, with a dollar-for-dollar phase-out beginning at $4,090,000 of qualifying purchases.⁹ That cap is shared across the group and allocated among members either by agreement or, in a consolidated return, by the common parent.¹⁰ Research credit expenses under Section 41(f) are aggregated the same way. Owners counting on each entity to claim its own full deduction will find the math disappointing.

Plan Disqualification Is the Worst Case

If a qualified plan fails coverage or nondiscrimination because the sponsor did not count employees from related entities, the plan can lose its tax-exempt status. Highly compensated employees must immediately include their entire vested balance in taxable income, distributions cannot be rolled over to an IRA or another qualified plan, and the trust itself owes tax on its earnings.¹¹ IRS correction programs exist, but they require voluntary disclosure and can involve significant corrective contributions. Running the parent-subsidiary and brother-sister tests early, with attribution factored in, is far cheaper than fixing a controlled group problem after a failed test surfaces it.

1
GovInfo. 26 USC 1563 – Definitions and Special Rules
2
eCFR. 26 CFR 1.1563-1 – Definition of Controlled Group of Corporations and Component Members and Related Concepts
3
Internal Revenue Service. Controlled and Affiliated Service Groups
4
Office of the Law Revision Counsel. 26 USC 1563 – Definitions and Special Rules
5
eCFR. 26 CFR 1.414(c)-2 – Two or More Trades or Businesses Under Common Control
6
Office of the Law Revision Counsel. 26 USC 414 – Definitions and Special Rules
7
Internal Revenue Service. Instructions for Forms 1094-C and 1095-C
8
Internal Revenue Service. Revenue Procedure 2025-26
9
Internal Revenue Service. Internal Revenue Bulletin 2025-45 – Revenue Procedure 2025-32
10
eCFR. 26 CFR 1.179-2 – Limitations on Amount Subject to Section 179 Election
11
Internal Revenue Service. Tax Consequences of Plan Disqualification