A partnership is the legal relationship that exists when two or more people co-own and run a business for profit. Under the Revised Uniform Partnership Act (RUPA), which nearly every state has adopted in some form, that relationship can arise even if the parties never signed anything, never used the word “partner,” and never intended to form a business entity at all. The definition of a partnership turns on economic reality: if you share control of a business and the right to its profits, the law likely treats you as partners, with everything that status carries, including joint responsibility for the business’s debts.1Office of the Law Revision Counsel. 26 U.S. Code 761 – Terms Defined
How the Law Defines a Partnership
Two bodies of law supply the definition, and they do not match perfectly.
State law, generally based on RUPA, defines a partnership as “the association of two or more persons to carry on as co-owners a business for profit.” The pivotal phrase is “co-owners.” Courts look at whether the parties share control and share profits, not at the labels they used or whether they filed paperwork. A handshake arrangement to run a food truck together, with profits split down the middle, is a general partnership even if neither person has ever heard the term.
The federal Internal Revenue Code goes broader. Section 761(a) treats as a partnership any syndicate, group, pool, joint venture, or other unincorporated organization that carries on a business or financial venture.1Office of the Law Revision Counsel. 26 U.S. Code 761 – Terms Defined The IRS can therefore classify an arrangement as a partnership for tax purposes even where state law would characterize it differently. If you are splitting profits from a shared business venture with someone, both the state and the federal government probably already see you as partners.
Types of Partnerships
Not every partnership carries the same consequences. The structure determines who manages the business, who faces personal liability, and what the state requires on the way in.
- General Partnership (GP). Every partner shares management authority, and every partner bears unlimited personal liability for the business’s debts. No state filing is required to create one, which is why many general partnerships form by accident when two people start working together for profit.2U.S. Small Business Administration. Choose a Business Structure
- Limited Partnership (LP). An LP has at least one general partner with full management authority and unlimited liability, plus one or more limited partners whose liability typically cannot exceed what they invested. Limited partners generally stay out of day-to-day operations; getting too involved can strip the shield. Forming an LP requires filing a certificate with the state.2U.S. Small Business Administration. Choose a Business Structure
- Limited Liability Partnership (LLP). An LLP shields every partner from personal liability for the partnership’s debts and for the misconduct of other partners. Professional firms like law practices and accounting firms often use this form. LLPs must register with the state.3U.S. Small Business Administration. Register Your Business
When people use the word “partnership” without qualification, they usually mean a general partnership. That is also the form the definition most readily captures by default, and the form that carries the most personal risk.
Why the Definition Matters: Authority and Personal Liability
In a general partnership, every partner acts as an agent of the business. Any partner can sign contracts, take on debt, and make commitments that bind the entire partnership, as long as the activity falls within the ordinary scope of the business. If your business partner orders $50,000 in inventory without consulting you, the partnership owes that money, and so do you personally.
Partners face joint and several liability for all partnership obligations. A creditor owed money by the partnership can pursue any single partner for the full amount, not just that partner’s proportional share. It does not matter whether you approved the transaction, knew about it, or benefited from it. Unpaid vendor bills, lease obligations, loans, and injury claims arising from a partner’s negligence in the course of business can all land on your personal doorstep.
Your personal assets, including your bank accounts, home equity, and investments, are not walled off from the business’s creditors. This exposure is the single biggest reason to think carefully before entering, or drifting into, a general partnership.
Forming a Partnership
A general partnership has almost no formal creation requirements. Two people can start one with a handshake, a verbal agreement, or simply by acting as co-owners. Corporations, LLCs, LPs, and LLPs all require registration with a state agency; a GP does not.
Even though a written agreement is not legally required, operating without one is a serious mistake. A partnership agreement sets each partner’s capital contribution, profit share, decision-making authority, and exit terms. Without one, state default rules fill the gaps, and those defaults rarely match what the partners actually intended. The most common surprise: profits and losses are split equally, no matter how much each person invested or how many hours they put in.
If the partnership operates under a name other than the partners’ legal names, many states require a “Doing Business As” (DBA) filing with the county or state.3U.S. Small Business Administration. Register Your Business Every partnership also needs an Employer Identification Number (EIN) from the IRS, whether or not it has employees. The EIN application is free and available online.4Internal Revenue Service. Get an Employer Identification Number
A good agreement also includes buy-sell provisions covering what happens when a partner dies, becomes disabled, retires, or wants out. These usually specify how the departing partner’s interest will be valued, through a fixed price the partners revisit periodically, a formula based on revenue or earnings, or an independent appraisal at the time. Without buy-sell terms, a partner’s exit can turn into an expensive legal fight or force the business to dissolve entirely.
What Partners Owe Each Other
Partners owe each other fiduciary duties. In plain terms, they have to deal honestly and put the partnership’s interests ahead of their own. RUPA breaks those duties into loyalty and care.
Duty of Loyalty
Loyalty prevents a partner from competing with the partnership, diverting business opportunities for personal gain, or entering transactions that create a conflict of interest. If you discover a potential deal within the partnership’s line of business, you have to bring it to the partnership first. Secretly profiting from the partnership’s resources or information is a breach that can expose you to damages and, in severe cases, lead to a court-ordered dissolution.
Duty of Care
The duty of care sits lower than many people expect. Under RUPA, it is limited to avoiding grossly negligent or reckless conduct, intentional misconduct, and knowing violations of the law. Ordinary business mistakes and honest errors in judgment generally do not count as a breach. The law recognizes that business decisions involve risk and does not punish partners for outcomes that simply did not work out.
Access to the Books
Partners have a right to inspect the partnership’s books and records at the principal office during normal business hours. Each partner is entitled to any information reasonably needed to exercise their rights and fulfill their duties, and that access extends to former partners for the period they were involved. A partner being shut out of the books is itself a red flag.
How Profits and Losses Are Split
The partnership agreement controls how income, gains, losses, and deductions are divided. For tax purposes, the Internal Revenue Code respects whatever allocation the agreement specifies, as long as it has “substantial economic effect,” meaning the split reflects real economic consequences to the partners rather than a paper arrangement built for tax savings.5Office of the Law Revision Counsel. 26 U.S. Code 704 – Partners Distributive Share
If the agreement is silent, or if an allocation lacks substantial economic effect, each partner’s share is determined by their overall interest in the partnership based on all the facts and circumstances.5Office of the Law Revision Counsel. 26 U.S. Code 704 – Partners Distributive Share Under most state default rules based on RUPA, that means equal shares regardless of what each partner contributed. A partner who put in $200,000 and a partner who put in $10,000 would split profits 50/50 unless the agreement says otherwise.
How a Partnership Is Taxed
A partnership does not pay federal income tax. Its income passes through to the individual partners, who report their shares on their personal returns.6Office of the Law Revision Counsel. 26 U.S.C. Subtitle A, Chapter 1, Subchapter K – Partners and Partnerships This pass-through structure avoids the double taxation that applies to C corporations, where the business pays tax on its profits and shareholders pay again on dividends.
Even though the partnership owes no income tax of its own, it must file Form 1065 each year as an information return reporting total income, deductions, gains, and losses.7Internal Revenue Service. About Form 1065, U.S. Return of Partnership Income For calendar-year partnerships, Form 1065 is due March 15 of the following year, with an automatic six-month extension available on Form 7004. The partnership issues a Schedule K-1 to each partner showing that partner’s share of income, deductions, and credits, which the partner then uses to complete their own return.8Internal Revenue Service. 2025 Instructions for Form 1065
One detail surprises many new partners: you owe tax on your allocated share of the partnership’s income whether or not the partnership actually distributes cash to you. If the business earns $100,000 and reinvests all of it, you still owe tax on your share.9Office of the Law Revision Counsel. 26 U.S. Code 702 – Income and Credits of Partner
General partners also owe self-employment tax on their share of the partnership’s net earnings. The combined rate is 15.3%, split between 12.4% for Social Security and 2.9% for Medicare, with an additional 0.9% Medicare surtax on self-employment income above $200,000 for single filers or $250,000 for joint filers.10Office of the Law Revision Counsel. 26 U.S.C. Subtitle A, Chapter 2 – Tax on Self-Employment Income Unlike employees, who split payroll taxes with an employer, partners pay the full amount themselves. Because no tax is withheld from distributions, partners generally make quarterly estimated tax payments to the IRS to cover both income and self-employment tax.11Internal Revenue Service. Estimated Tax
Filing Form 1065 late is more expensive than many small partnerships expect. The penalty is $195 per partner for each month or partial month the return is late, up to 12 months, with annual inflation adjustments on top.12Office of the Law Revision Counsel. 26 U.S.C. 6698 – Failure to File Partnership Return A five-partner firm that files six months late can rack up several thousand dollars in penalties, even though the partnership itself owes no tax.
How a Partnership Ends
A partnership can end in several ways: the partners agree to wrap things up, a term in the agreement expires, a partner withdraws or dies, or a court orders dissolution. Dissolution does not immediately end the business. It starts a process called winding up, during which the partnership collects what it is owed, finishes outstanding work, and pays its debts.
The order of payment matters. Creditors are paid first, before any partner receives a distribution. If partnership assets are not enough to cover its debts, the partners in a general partnership remain personally liable for the shortfall. Whatever is left after obligations are settled is distributed to the partners according to the agreement, or equally if the agreement does not address the point. Until third parties know the partnership has ended, any partner can generally still bind it to new obligations, so written notice to known creditors and a published notice to the public help close that window.
The through-line from definition to dissolution is the same: a partnership is defined by shared ownership of a business for profit, and almost everything that follows, from liability to taxes to the way the business ends, flows from that one fact. If you are in that position with someone, treat the arrangement as what the law already considers it, and put the terms in writing before the defaults decide them for you.