Your Startup Sold Its Foreign Subsidiary in October. Why December Can Still Affect U.S. Tax.

Imagine a U.S. startup owns a development subsidiary overseas.

The startup sells the foreign subsidiary in October. The buyer takes over. The seller no longer owns it.

It would be reasonable to assume that the seller's U.S. tax exposure to the subsidiary stopped at closing.

Starting with foreign corporation tax years beginning after December 31, 2025, that assumption can be wrong.

01The old year-end rule changed

Under the prior rules, ownership on the relevant last day of a controlled foreign corporation's tax year played an outsized role in determining who picked up certain CFC income.

Congress changed that.

A U.S. shareholder can now have subpart F income or net CFC tested income, commonly called NCTI under the post-2025 rules, based on the period during the year that it owned the CFC stock.

So if a U.S. company owns a foreign subsidiary from January through October and then sells it, the U.S. tax consequences do not necessarily disappear simply because the seller no longer owns the subsidiary on December 31.

For these rules, ownership generally means stock owned directly or indirectly under IRC §958(a).

02The strange part: December can still matter

Suppose a U.S. startup owns 100% of a calendar-year foreign subsidiary and sells the subsidiary to an unrelated U.S. buyer on October 15.

The foreign company remains a CFC after the transaction.

Under the IRS's proposed regulations, the seller's share of certain CFC income is generally determined using a daily-proration approach.

But daily proration does not necessarily mean someone closes the books on October 15 and calculates only the income actually earned while the seller owned the company.

Instead, the CFC's income for its tax year can be determined first and then allocated based on the period the shareholder owned the stock.

That creates a counterintuitive result:

You can sell the foreign subsidiary in October and still care what happens inside that company in November and December.

A particularly profitable fourth quarter could affect an allocation to someone who stopped owning the subsidiary months earlier.

That is not usually what founders expect when they hear that the subsidiary has been sold.

03Sometimes the CFC year can close early

The proposed regulations also contain year-closing rules that can change this result.

If an ownership change causes a foreign corporation to become or cease to be a CFC, the proposed rules generally require its tax year to close at the end of that event day.

A different rule may apply when the company remains a CFC but there is a significant ownership change.

In certain transactions where U.S. shareholder ownership decreases by more than 50 percentage points, the proposed regulations may allow an election to close the CFC's tax year at the end of the event day.

That can produce a very different result from allocating income using the CFC's full tax year.

But the election comes with conditions. Depending on the ownership structure, it may require coordination among U.S. shareholders, a written binding agreement and an information statement filed with the IRS. Transactions involving several CFCs can also bring consistency requirements.

In other words, this may be something to address while the deal is being structured, not something to discover when preparing the tax return months later.

04The transaction structure matters

A sale involving a foreign subsidiary does not always produce the same result.

If the U.S. startup sells the stock of its foreign subsidiary, the seller may still have a partial-year CFC inclusion even though it no longer owns the subsidiary at year-end.

If the transaction causes the foreign company to stop being a CFC altogether, the proposed regulations generally call for the CFC's year to close at the end of that event day.

If the foreign company remains a CFC but there is a large enough ownership shift, an elective year closing may be available depending on the facts.

And if the founders are simply selling their shares of the U.S. parent, that is not automatically the same fact pattern. The ownership chain and acquisition structure need to be reviewed before assuming the new rules apply in the same way.

The same is true when several foreign subsidiaries move as part of one transaction. The analysis may extend across the deal rather than stopping with one entity.

That is why "we sold the company in October" is not enough information to determine the tax result.

The questions are what was actually sold, who owned the foreign corporation before and after closing, whether it remained a CFC, the ownership percentages involved, and what happened inside the foreign company during the year.

05This can become a deal issue before it becomes a tax-return issue

There is another practical problem.

If the seller's tax calculation can depend on the foreign subsidiary's full-year income, the seller may need financial and tax information from a company it no longer owns.

Who provides that information? When? What happens if the buyer changes accounting practices, restructures operations or generates substantial income after closing?

Those questions can become much harder to solve after the purchase agreement has already been signed.

And the year-closing election, when available, may require decisions and coordination that cannot simply be recreated months later during tax preparation.

06Before a transaction involving a foreign subsidiary closes

For deals involving a foreign subsidiary, the tax team should know about the transaction before closing.

The old shorthand of asking who owns the CFC at year-end is no longer enough.

For post-2025 foreign corporation tax years, ownership during the year matters too. And depending on the transaction, the difference between daily proration and closing the CFC's tax year at the transaction date can materially change the U.S. tax result.

This article focuses on the new subpart F and NCTI allocation rules. Other CFC provisions, including IRC §956, continue to have their own timing rules.

The answer ultimately depends on the ownership chain, buyer, transaction structure, CFC status and foreign subsidiary's income.

This article is general information, not tax or legal advice. The rules are fact-specific, change over time, and depend on details unique to your company. Talk to us about how they apply to your situation.