A new Fifth Circuit ruling may reshape how self‑employment tax applies to U.S. individuals invested in foreign partnerships — a group often overlooked in domestic commentary. The Sirius Solutions decision shifts attention back to the statutory text of Section 1402 and raises fresh questions about how the limited partner exception should apply when U.S. taxpayers hold interests in foreign vehicles that resemble traditional limited partnerships.

Last year, I warned about the Tax Court’s Soroban decision and the serious self-employment tax risks it posed for U.S. investors and managers using foreign funds and limited partnership structures. In Soroban, the IRS looked past legal labels and attacked active participants in the business, threatening the valuable limited partner exception from self-employment tax.

A new appellate decision in Sirius Solutions LLLP v. Commissioner, No. 24-60240 (5th Cir. 2026), may have materially altered that landscape. While most Sirius commentary has focused on domestic fund structures and self-employment tax, the international implications for U.S. persons in foreign vehicles deserve closer attention — and that is the focus of this article.

Material tax exposure often arises from the interaction between U.S. tax rules and foreign structures that were not designed with the U.S. tax system in mind.

Why The Limited Partner Exception Matters

The self-employment tax rules generally subject business income earned by sole proprietors and partners to Social Security and Medicare taxes under Section 1401 of the Internal Revenue Code.

It’s a hefty tax at 15.3%. Congress created an important exception, however. Section 1402(a)(13) excludes the distributive share of a limited partner from self-employment tax, other than certain guaranteed payments for services.

Although the limited partner exception has existed since 1977, courts and the IRS have struggled to apply it to modern business structures such as LLCs and LLPs. These structures did not exist when Congress drafted the exception almost 50 years ago. The IRS argues that substance should prevail over form when applying the exception. Under that view, a taxpayer........

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