CFC Attribution Rules: Are You a US Shareholder?

The One Big Beautiful Bill Act (OBBBA) changed who counts as a US shareholder starting with the 2026 tax year. Congress restored IRC 958(b)(4), the provision the Tax Cuts and Jobs Act (TCJA) had repealed in 2017, and a foreign parent's stock in a foreign sister company stops being attributed down to the US subsidiary. Ownership decides all of it, & that means the 10% test, the three counting methods, and the rule Congress just changed for 2026.

Who Is a US Shareholder and When Is a Foreign Corporation a CFC?

A US shareholder under IRC 951(b) is a US person owning 10% or more of a foreign corporation's voting power, or 10% or more of the value of its shares. Either prong is enough. The corporation is a CFC under IRC 957(a) when those shareholders own more than 50% of its vote or value on any day of the year.

The value prong is newer than the vote prong. TCJA added it for taxable years of foreign corporations beginning after December 31, 2017, and for the tax years of US shareholders in which or with which those foreign corporation years end. Before that, someone could hold nonvoting preferred worth millions and never trip the line. Run the vote and value tests separately every year, because a person can clear one and miss the other.

Only people who independently clear 10% count toward the more than 50%. Ten US persons at 3% each never add up to a CFC. A single day of majority US shareholder ownership, during a closing or a restructuring, is enough for that period. For what a CFC is and what happens once one exists, start with our CFC rules pillar.

What Are the Three Ways Ownership Is Tested Under Section 958?

Section 958 tests ownership three ways. Direct ownership under 958(a)(1)(A) covers stock held in your own name. Indirect ownership under 958(a)(2) covers stock held through a foreign corporation, partnership, trust or estate. Constructive ownership under 958(b) applies the Section 318 family and entity attribution rules. Clearing 10% under any one of the three makes you a US shareholder.

A person can be a US shareholder through constructive ownership & still never get a Subpart F or net CFC tested income inclusion from that same stock. Constructive ownership decides who you are. It doesn't always decide what you're taxed on. That works because IRC 951(a)(1) and the net CFC tested income pro rata share rules both start from stock owned under 958(a), so constructive stock counts for status and reporting and never enters the inclusion computation at all.

How Does Constructive Ownership Under Section 318 Pull In Family Members?

Constructive ownership under IRC 958(b) applies the Section 318 attribution rules with modifications. The Section 318 family rule treats stock owned by a spouse, children, grandchildren and parents as also owned by the individual. Siblings are not included. Cross 10% that way and you are a US shareholder.

IRC 958(b)(1) is a narrow modification. It switches off the 318(a)(1)(A) family rule in one direction only, so stock owned by a nonresident alien individual is not treated as owned by a US citizen or resident alien. It leaves family attribution running the other way alone, and it does not touch the 318(a)(2) and 318(a)(3) entity rules. Section 318 still attributes stock to and from partnerships, estates, trusts and corporations based on a partner's, beneficiary's or shareholder's interest.

The IRS follows attribution rules, regardless of whether the person on paper ever felt like an owner. A family member who has never seen the foreign corporation's financials or sat on its board can still be the person the IRS expects to file.

What Is Downward Attribution, and Did OBBBA End It for 2026?

Downward attribution is stock attributed from a foreign person down to a related US person, and for tax years 2017 through 2025 it created CFCs where nobody owned anything economically. OBBBA ended that for 2026 by restoring IRC 958(b)(4), and a narrower rule under new IRC 951B took its place.

TCJA repealed IRC 958(b)(4), the provision that had blocked attribution of stock from a foreign person to a US person. With that block gone, stock a foreign parent held in a foreign subsidiary was attributed down to a US subsidiary of the same parent, and the foreign sister company became a CFC. TCJA section 14213 made the repeal effective for the last taxable year of a foreign corporation beginning before January 1, 2018, which for a calendar-year company is 2017.

Congress reversed that. The One Big Beautiful Bill Act, P.L. 119-21, enacted July 4, 2025, restored IRC 958(b)(4) for taxable years of foreign corporations beginning after December 31, 2025. For the 2026 tax year forward, a foreign parent's stock in a foreign sister company is no longer attributed down to the US subsidiary, and that sister company is no longer a CFC on those facts alone.

The same act put a narrower rule in its place. New IRC 951B builds a second track for what it calls a foreign controlled United States shareholder, meaning a US person that would be a US shareholder if the 10 percent test were run at more than 50 percent, applying 958(b) without paragraph (4). A foreign corporation that would be a CFC when tested against those shareholders is a foreign controlled foreign corporation, and Subpart F and net CFC tested income inclusions follow. So downward attribution still exists, at a much higher ownership threshold and under a different label.

The law simply started attributing that same stock to a different person. Ordinary foreign-parented groups with a US presence picked up Form 5471 obligations for 2017 through 2025 that they had no economic reason to expect.

The years in between still matter. Tax years 2017 through 2025 run under the repeal, and a missed Form 5471 for any of those years keeps the assessment statute open under IRC 6501(c)(8) until the form is filed. If you are cleaning this up, start with 2017. Run the section 8.04 exception first. An unrelated constructive US shareholder of a foreign-controlled CFC owed nothing for those years, and there is no point building a package that was never due.

Does Rev. Proc. 2019-40 Still Help an Accidental CFC Shareholder?

Rev. Proc. 2019-40 helps a US person who cannot get information about a foreign corporation, and it never turns on whether that person is an officer, director or controlling shareholder. Its main safe harbor lets you treat a foreign corporation as not a CFC when you lack the information to conclude otherwise.

Section 4 of the revenue procedure sets out that safe harbor, and section 4.02 says it does not apply to a foreign corporation that is a US-controlled CFC. The IRS will accept your determination that a foreign corporation does not meet the section 957 ownership requirements if you have no actual knowledge, statements received, or reliable publicly available information sufficient to determine that those requirements are met, and if you make the inquiry the procedure describes of any top-tier foreign entity you own directly. That inquiry asks the top-tier entity whether it meets the section 957 ownership requirements and what foreign and domestic entities it owns.

Sections 5 and 6 set out the alternative-information safe harbors. They let an unrelated section 958(a) US shareholder of a foreign-controlled CFC, one for which there is no related section 958(a) US shareholder, determine Subpart F, net CFC tested income and section 965 amounts from financial statements or internal records when the Reg. 1.952-2 and IRC 964 information is not readily available. Section 7 then switches off IRC 6038 and IRC 6662 penalties for positions taken under those safe harbors.

There's a catch for a purely constructive shareholder. That alternative-information relief runs to a section 958(a) shareholder, and a purely constructive US shareholder owns no 958(a) stock at all. The revenue procedure does extend the same alternative information to an unrelated constructive US shareholder for amounts reported on Form 5471, and a constructive shareholder can use it. Confirm your facts fit a defined category before you treat a filing as excused.

What Happens Once You Are a US Shareholder of a CFC?

Being a US shareholder of a CFC puts you in Category 5 on Form 5471, and two exceptions in the instructions can lift the filing off you entirely. Whether it triggers income is a separate question and it turns on how the stock is owned. A person who is a US shareholder purely by constructive ownership includes nothing, and may not have to file at all.

Subpart F under IRC 951(a)(1) reaches only a US shareholder who owns stock within the meaning of IRC 958(a), meaning directly or indirectly, and net CFC tested income under IRC 951A works off the same 958(a) pro rata share under Treas. Reg. 1.951A-1(c). That is the practical difference between 958(a) and 958(b), and it is worth getting right before anyone reports income they don't owe. Which regime picks up which dollars is the subject of our Subpart F and GILTI comparison.

Category 5 is also not one filing. The Form 5471 instructions split it into 5a, 5b and 5c. A 5b filer is an unrelated section 958(a) US shareholder of a foreign-controlled CFC, a 5c filer is a related constructive US shareholder of one, and both complete far fewer schedules than a 5a filer. Two exceptions remove the filing entirely, and both are worth checking before anyone assembles a package. No Category 5 filing is required when no US shareholder owns 958(a) stock in the corporation on the last day it was a CFC and the corporation is a foreign-controlled CFC. Nor is any filing required from an unrelated constructive US shareholder, meaning a US shareholder of a foreign-controlled CFC who owns no 958(a) stock and is not related to it under section 954(d)(3) principles. That second one comes from section 8.04 of Rev. Proc. 2019-40, and it is the exception most foreign-parented groups needed for 2017 through 2025.

Family arrangements and multinational holding structures create these obligations for people who never thought of themselves as international taxpayers. The penalty exposure for a missed Form 5471 exists regardless of whether the person understood they were a shareholder, and it starts at $10,000 per form per year under IRC 6038(b)(1).

Family stock, a foreign parent, or a foreign entity anywhere in the ownership chain all change the 2026 answer. Our international tax team sorts out who the US shareholders actually are. Contact TS CPA for a free consultation. We respond within the same day.

Official IRS and Government Sources

• IRC Section 951, Amounts Included in Gross Income of United States Shareholders
• IRC Section 951B, Amounts Included in Gross Income of Foreign Controlled United States Shareholders
• IRC Section 957, Controlled Foreign Corporations
• IRC Section 958, Rules for Determining Stock Ownership
• IRC Section 318, Constructive Ownership of Stock
• IRC Section 6038, Information Reporting With Respect to Certain Foreign Corporations
• One Big Beautiful Bill Act, P.L. 119-21, Section 70353
• Rev. Proc. 2019-40
• IRS About Form 5471