For years, tax advisors have told clients a simple story about the limited partner exception to self-employment tax: form a state-law limited partnership (or LLLP), give someone limited liability, and their distributive share is exempt from SE tax under IRC §1402(a)(13). That story just got a lot more complicated.
In January 2026, the Fifth Circuit seemed to bless the simple version. In Sirius Solutions, L.L.L.P. v. Commissioner, a divided panel held that "limited partner, as such" means exactly what state law says it means: a partner with limited liability, full stop. The court rejected the Tax Court's more searching "functional analysis" test from Soroban Capital Partners and Denham Capital Management, which looks at what a partner actually does, not just their state-law label.
Then, on August 12, 2026, the same panel reversed course. Responding to the government's petition for rehearing, the Fifth Circuit withdrew its January opinion entirely and issued a substitute, now captioned K Alain, L.L.L.P. v. Commissioner. The new standard: a limited partner is someone who "plays no significant role in managing or running a business." State-law liability status is no longer the deciding factor; the court now treats "limited partner" as a federal question turning on the partner's actual role in the enterprise.
That's not quite the Tax Court's functional test from Soroban, and the Fifth Circuit didn't draw a bright line for where "some participation" ends and "a significant role in managing" begins. But it's much closer to the IRS's preferred reading than the January opinion was, and it means the label on the partnership agreement is no longer enough to win this argument on its own.
Who's exposed? Any client where an active manager, executive, or day-to-day decision-maker holds a "limited partner" interest, which is common in professional services firms, fund management LLLPs, and multi-tier LLC/LLP structures built specifically to sidestep SE tax, is now sitting on a functional-role question rather than a settled liability question. The more involved that partner is in running the business, the harder it will be to defend the exemption if challenged.
What to do before filing season: Pull every client structure currently claiming the §1402(a)(13) exception and ask, honestly, how involved each "limited" partner actually is in management. Document the passive ones. Flag the active ones for a conversation about whether continued reliance on the exception is defensible, whether guaranteed payments should be restructured, or whether an amended return is the more conservative path for open years.
One more wrinkle: this fight isn't over. The taxpayers in K Alain have 45 days from the August opinion to seek further rehearing, and the same underlying question is pending in the First and Second Circuits in Denham and Soroban. A circuit split is a real possibility. That's not a reason to wait, but rather it's a reason to get client exposure mapped now, before the next ruling changes the math again.