Two friends buy a short-term rental together. They split everything, from income and expenses to responsibilities, 50/50. One manages the bookings while the other handles repairs. They never wrote up any agreement, registered an LLC, or created any paperwork at all.
Did these friends accidentally create a partnership with federal filing requirements?
Now make it more complicated. What if those two friends are married? What if they’re flipping houses instead of renting them? What if one spouse does all the work while the other occasionally helps with administrative tasks?
These are real questions that come across the desk of tax professionals every week. While they might seem straightforward, the answers are anything but simple or academic Partnership status affects filing requirements, basis calculations, elections, self-employment tax, audit procedures under the BBA, and the availability of numerous Subchapter K provisions. That’s why correctly identifying whether a partnership exists is the first step in any partnership analysis.
In episode 31 of Tax in Action, Jeremy Wells, EA, CPA, tackles this tough question in small business taxation: When does co-ownership cross the line into a partnership under federal tax law? Drawing from IRC §761(a) and §7701, Treasury regulations, and Supreme Court cases dating back to the 1940s, Jeremy builds a practical framework you can apply to client situations starting today.
Determining whether a co-owned activity is a partnership requires more than checking if someone filed an LLC with the state. You need to analyze the shared profit motive, business activity, and genuine intent. The analysis is shaped by decades of court-tested criteria. You also need to understand the distinct exceptions available to married couples.
Get this analysis right, and you’ll meet reporting requirements while positioning clients for partnership planning opportunities. Get it wrong, and you face unfiled return penalties, missed planning strategies, or both.
The Federal Definition Casts a Wide Net (With Important Limits)
To determine if your client’s co-owned activity is a partnership, you first need to understand how broadly federal tax law defines the term and where it draws the line.
IRC §761(a) defines “partnership” to include syndicates, groups, pools, joint ventures, and other unincorporated organizations (excluding corporations, trusts, and estates). That’s remarkably broad. As Jeremy explains, essentially any business-like activity with more than one participant could qualify. Add the companion definition in IRC §7701(a)(2) and Treasury regulations, and you have a framework that captures far more arrangements than most people realize.
There’s also the familiar default rule: Under Reg. §301.7701-3(b), a domestic eligible entity with two or more members that hasn’t filed a corporate election is treated as a partnership. This is where we get “multi-member LLC equals partnership.” For foreign entities, you need to check whether any member lacks limited liability, but the domestic rule is straightforward.
Despite this broad sweep, the regulations carve out two important exceptions that do not create a separate entity for federal tax purposes:
- A joint undertaking merely to share expenses
- Mere co-ownership of property (even income-producing property)
That second exception matters most in everyday practice. Two unrelated people can buy a rental property together, split the income and expenses, and that alone doesn’t necessarily create a partnership.
Jeremy shares an example from Laura and Noel Cunningham’s textbook, The Logic of Subchapter K. Two people co-own a taxi cab. Each drives it 12 hours a day, tracking their own fares and expenses separately. No partnership exists because there’s no joint profit motive. What you earn during your shift has nothing to do with what I earn during mine.
But change the facts and lease that cab to a third party who pays both owners. Now you’ve introduced a collective profit motive, and it looks like a partnership.
The Cunninghams identify two key features: business activity and sharing of profit. When both exist, you likely have a partnership. When either is missing, you probably have mere co-ownership.
This is where things get tricky. A single rental property split between two friends is probably mere co-ownership. But if they offer concierge services for an extra fee or they’re building a portfolio of rentals and managing them like a business, each additional fact pushes the activity toward partnership territory.
As Jeremy emphasizes repeatedly, federal tax law, not state law, controls this determination. You can register an LLC, file articles and get a certificate of formation, but none of these facts, standing alone,
determines whether a partnership exists for federal tax purposes. As the Supreme Court established 75 years ago, states can create entities on their books, but they can’t dictate federal tax consequences.
When Partnerships Actually Form
Knowing a partnership can exist is one thing. Knowing when it forms and triggers filing obligations is another matter entirely. It has nothing to do with filing paperwork at the Secretary of State’s office.
A partnership forms for federal tax purposes when participants join capital or services together with the intent to conduct an enterprise or business. Courts generally look for both genuine intent to carry on a business together and some actual contribution of capital or services.
Plans, discussions, and handshake agreements don’t count. Something tangible must go into the pot.
This framework comes from two landmark Supreme Court decisions every practitioner should know.
Tower v. Commissioner (1946) laid the foundation. The Supreme Court held that a partnership forms when people join “their money, goods, labor, or skill for the purpose of carrying on a trade, profession, or business” with a “community of interest in the profits and losses.” The critical question: whether the partners “really and truly intended to join together for the purpose of carrying on business and sharing in the profits or losses.”
Tower also drew a bright line between state and federal authority. As the Court stated, a state “cannot, by its decisions and laws governing questions over which it has final say, also decide issues of federal tax law.”
Culbertson v. Commissioner (1949) clarified what Tower meant. Lower courts misread Tower as requiring some minimum threshold of capital or services. The Supreme Court corrected this, saying, “The question is not whether the services or capital contributed by a partner are of sufficient importance to meet some objective standard,” but whether “considering all the facts, the parties in good faith and acting with a business purpose intended to join together in the present conduct of the enterprise.”
Culbertson produced the factors courts use to assess intent, and practitioners should memorize these criteria:
- The agreement and the parties’ conduct in executing it
- Whether each participant genuinely participates or is just a name on paper
- Testimony of disinterested persons (would vendors or advisors see this as a partnership?)
- The relationship of the parties
- Their abilities and capital contributions
- Actual control of income and how it’s used
- Any other facts showing true intent
Jeremy notes that family partnership cases of the 1940s-1960s drove much of this development. Families were forming partnerships primarily for tax benefits. Courts had to determine whether these were genuine business partnerships or just tax avoidance vehicles. When the intent was purely to dodge taxes rather than to operate an enterprise, courts rejected partnership status.
Sparks v. Commissioner (1986) adds practical guidance. The Tax Court held that startup discussions, soliciting contributions, negotiating with third parties, and even incurring expenses were “pre-operating activities,” not partnership formation. The partnership didn’t form until members’ capital interests vested, meaning contributions were made and ownership interests received.
The practical takeaway is to document everything. Jeremy emphasizes that small business owners are terrible at this, and tax advisors must encourage better practices. A partnership or operating agreement that records when contributions were made and the ownership interests received establishes the formation date, not the LLC filing, planning meeting, or domain registration.
Three Ways to Avoid Partnership Treatment
Once you’ve determined a partnership exists, the next question is whether an exception allows the parties to sidestep partnership reporting. Three pathways exist, and practitioners regularly confuse them.
Electing Out of Subchapter K
Under IRC §761(a), members of an unincorporated organization can elect out of Subchapter K treatment if they can determine their incomes individually and the activity involves:
- Investment purposes only
- Production, extraction, or use (but not sale) of joint property
- Securities underwriting over a short period
But the catch is that this election only removes Subchapter K rules. It doesn’t exempt the activity from any other IRC provision.
Jeremy highlights Cokes v. Commissioner (1988) as the cautionary tale. A widow inherited her husband’s interest in an oil venture that had elected out of Subchapter K. She never attended meetings, voted, drilled wells, or supervised operations. Her involvement was zero beyond holding an interest. Still, the Tax Court held her income was from a trade or business, subject to self-employment tax under IRC §§1401 and 1402. The partnership remained a partnership, just not subject to Subchapter K.
Qualified Joint Venture for Married Couples
The first spousal exception is available only to couples filing jointly who meet all three requirements:
- The spouses are the only members
- Both materially participate under IRC §469(h)
- Each reports their share as if operating as a sole proprietor (separate Schedules C (or F) and separate Schedules SE)
This splits what would be a partnership into two sole proprietorships for reporting, eliminating Form 1065.
A critical limitation to be aware of is the qualified joint venture is NOT available if spouses operate through an LLC. If they registered an LLC, this door is closed.
There’s no form to file. Spouses simply submit separate schedules with their joint return. The election continues while requirements are met. Revocation needs IRS permission.
Community Property LLCs
The second spousal exception applies when there IS an LLC, exactly where the qualified joint venture fails. But it only works in nine community property states: Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington, and Wisconsin.
To be eligible, the LLC must be wholly owned by spouses as community property with no corporate election filed. When met, Rev. Proc. 2002-69 lets spouses report the activity as either a partnership or a disregarded entity.
This isn’t an election, so there’s no form, statement, or revocation. It’s simply a choice the IRS respects. Spouses can theoretically change annually (though Jeremy says they probably shouldn’t).
Your Two-Step Framework for Partnership Determination
Jeremy distills everything into a practical framework you can apply immediately.
Step 1: Does a partnership exist?
Ask these questions in order:
- Are there two or more distinct owners? (Not an individual and their disregarded entity. They have to be two separate taxpayers)
- Are they merely co-owning property, or operating a business together?
- Is there a shared profit motive? Do they act like business co-owners or like investors holding the same asset?
The more parties look like business owners running an enterprise together, the more likely a partnership exists.
Step 2: Does an exception apply?
Check for:
- §761(a) election out of Subchapter K
- Qualified Joint Venture under §761(f) (spouses, joint return, no LLC)
- Community Property LLC under Rev. Proc. 2002-69 (spouses, community property state, LLC)
Key Takeaways for Tax Professionals
- Shared property doesn’t create a partnership. Shared business activity does. One rental is probably co-ownership. A portfolio with services looks different.
- State entity formation doesn’t control federal partnership status. The Supreme Court settled this in 1946.
- Partnerships form when participants contribute capital or services in exchange for ownership interests, not when they form an LLC or buy a domain. Document that moment.
- Push clients toward written agreements. Small business owners resist this. Partnership or operating agreements that record contributions and formation dates are essential.
- Don’t confuse the spousal exceptions. Qualified joint ventures and community property LLC rules are completely separate regimes for different situations.
- Electing out of Subchapter K doesn’t avoid self-employment tax or any other IRC provision.
These determinations have real consequences. Get it right, and you’ve met reporting requirements while positioning clients for planning opportunities. Get it wrong, and you face unfiled returns, unexpected self-employment tax, or missed savings.
If you’re ready to dive deeper, listen to the full episode of Tax in Action for all the case law details, regulatory citations, and Jeremy’s complete analytical framework. In the next episode, Jeremy examines who qualifies as a partner and tackles the increasingly important question of which partners face self-employment tax.