A co-owner is any person who shares legal title to an asset with at least one other person. In real estate, that shared title can take one of four main forms under U.S. law, and the form controls the questions that matter most: whether your share passes to your heirs or automatically to the other owners when you die, whether a creditor chasing one owner can reach the property, and how you get out if the arrangement stops working. Understanding what a co-owner is starts with understanding which of those four structures applies to you.
The Four Forms of Co-Ownership
Tenancy in Common
Tenancy in common is the default in most places. If a deed names multiple owners without specifying anything else, the law usually presumes this arrangement. Each owner holds a separate, undivided interest. Everyone can use the whole property, even though nobody owns a specific physical piece of it.
Shares do not have to be equal. One person might hold 70% while two others split the remaining 30%. Each owner can sell, gift, or mortgage their share without the others’ permission, and each can leave their share to anyone they choose in a will. There is no right of survivorship. When a tenant in common dies, their interest passes through their estate to their heirs or named beneficiaries, not to the surviving co-owners.
That flexibility comes with friction. A new co-owner who buys or inherits someone’s share may be a stranger to the others, and the ownership group can shift in ways nobody anticipated at the start.
Joint Tenancy With Right of Survivorship
Joint tenancy ties co-owners together more tightly. Every joint tenant holds an equal, undivided interest, and when one owner dies, that share automatically passes to the surviving joint tenants rather than going through probate or following a will. This right of survivorship is the reason most people choose joint tenancy in the first place.
Creating a valid joint tenancy requires four conditions, traditionally called the “four unities.” Each owner must receive their interest at the same time, through the same document, in equal shares, and with equal rights to possess the whole property.1Legal Information Institute. Joint Tenancy If any of those conditions breaks down, the joint tenancy converts into a tenancy in common. This commonly happens when one joint tenant sells or transfers their share. The transaction destroys the unities of time and title, so the new owner holds their interest as a tenant in common while the remaining original owners stay joint tenants with each other.
One detail surprises people: a joint tenant can sever the arrangement unilaterally. No one needs to agree. A single conveyance to a third party is enough. If you’re relying on the right of survivorship as part of your estate plan, any co-owner can eliminate it at any time without telling you.
Tenancy by the Entirety
Tenancy by the entirety is available only to married couples and is recognized in most states, though a handful also extend it to domestic partners.2Legal Information Institute. Tenancy by the Entirety It works like joint tenancy in one crucial respect: when one spouse dies, the survivor automatically receives full ownership. It also adds a layer of protection joint tenancy lacks.
Neither spouse can sell, mortgage, or transfer the property without the other’s consent. That mutual-consent requirement also shields the property from creditors who have a claim against only one spouse. If your spouse owes money on a credit card or gets sued personally, a creditor generally cannot force the sale of property held as tenants by the entirety to satisfy that debt. The protection has limits. Federal tax liens are a notable exception. The U.S. Supreme Court ruled in United States v. Craft (2002) that the IRS can attach a lien to entirety property even when only one spouse owes the tax debt. Joint debts both spouses share can also reach the property.
Community Property
Nine states use a community property system: Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington, and Wisconsin. In these states, most assets either spouse earns or acquires during the marriage belong equally to both spouses, regardless of whose name is on the title or who earned the income.3Internal Revenue Service. IRM 25.18.1 – Basic Principles of Community Property Law
Property you owned before marriage, along with gifts and inheritances received by one spouse alone, typically stays separate. The tricky part is that separate property can become community property if it gets mixed with marital funds or if both spouses contribute to it over time. At divorce, community property states start from a presumption of equal division, though not all enforce a strict 50/50 split. Some allow judges to divide property in whatever way they consider fair, which can produce unequal results.
What Every Co-Owner Can Do (and Owes)
Regardless of the ownership form, every co-owner has the right to use and occupy the entire property. A co-owner with a 20% interest can walk through the same front door and use the same rooms as the co-owner with 80%. No one can lock out another co-owner or restrict them to a certain part of the property.
Rental income follows the ownership share. A tenant in common with a 40% interest gets 40% of the rent; joint tenants split equally. The same proportional logic applies to expenses. Co-owners share the cost of property taxes, insurance, mortgage payments, and necessary maintenance according to their interests. When one co-owner covers more than their share, they can typically seek reimbursement from the others, though enforcing that right often requires legal action.
If one co-owner physically excludes another from the property by changing the locks, refusing entry, or otherwise blocking access, that’s called an ouster. The excluded owner can go to court to regain access and recover damages, usually measured as their proportionate share of the property’s fair rental value for the period they were locked out. Proving an ouster generally requires showing that you demanded access and were refused.
Improvements are where disputes get ugly. If you pour money into renovating a shared property without the other owners’ agreement, you cannot simply send them a bill for their share. Courts distinguish between necessary repairs that preserve the property and voluntary improvements that enhance it. For necessary repairs, co-owners generally owe contribution. For improvements like a kitchen remodel or a new deck, you’re in weaker territory. In a partition proceeding, a court may credit you for the increase in property value your improvements created, but it typically caps that credit at either the cost you spent or the actual value added, whichever is lower. Outside of partition, some courts have held that co-owners have no right to reimbursement for improvements absent an agreement.
Mortgage Liability When You Sign Together
When co-owners take out a mortgage together, each person who signs the loan is fully liable for the entire balance, not just their ownership share. If one co-owner stops making payments, the lender does not care about your internal agreement. The other co-owners must cover the shortfall or face foreclosure and credit damage affecting everyone on the loan. Late and missed payments hit every borrower’s credit report equally.
The co-owner who keeps paying to protect the property can seek reimbursement from the one who stopped, but collecting on that claim is a separate fight.
Getting Out of Co-Ownership
The cleanest exit is voluntary. All co-owners agree to sell and split the proceeds according to their interests, or one co-owner buys out the others. A buyout requires agreement on the property’s value, which usually means hiring an independent appraiser. If you have a co-ownership agreement with a pre-set valuation method, this step becomes much simpler.
When co-owners cannot agree, any of them can file a partition action asking a court to force a resolution. Courts can order two types. A partition in kind physically divides the property into separate parcels, giving each owner a piece they hold outright. That works for large tracts of land but is impractical for a single house. More commonly, the court orders a partition by sale: the property is sold and the proceeds are divided among the owners according to their interests, with credits and offsets for unequal contributions to expenses or improvements. Partition actions are expensive, and court-ordered sales tend to produce below-market prices because they lack the negotiating leverage of a voluntary listing. Mediation is usually cheaper, faster, and more likely to produce a price everyone can live with.
Death ends co-ownership differently depending on the form. In a joint tenancy or tenancy by the entirety, the right of survivorship means the deceased owner’s interest passes automatically to the surviving owners. No probate, no will interpretation, no delay. In a tenancy in common, the deceased owner’s share goes to their estate and is distributed according to their will or state intestacy laws. The surviving co-owners have no automatic claim to that share and may end up sharing the property with the deceased owner’s heirs. Inherited co-ownership is one of the most common sources of partition disputes.
Why a Written Agreement Matters
The law fills in gaps when co-owners don’t have a written agreement, but it fills them in with default rules that may not match what you actually want. A co-ownership agreement lets you set the terms before a dispute forces a judge to do it for you. At minimum, a useful agreement addresses:
- Who pays what share of the mortgage, taxes, insurance, and maintenance, and what happens if someone falls behind.
- Whether all owners will live in the property, whether it will be rented, and how decisions about use are made.
- Whether the remaining owners get the chance to buy a departing owner’s share before it goes to an outsider, and on what timeline.
- How the property will be valued for a buyout and how payment will work.
- Whether disagreements go to mediation or arbitration before anyone files a lawsuit.
- What events allow or require a sale: death, divorce, bankruptcy, or simply one owner wanting out.
Without these provisions in writing, every disagreement becomes a negotiation from scratch, and the fallback is a partition action nobody wants.
Tax Consequences Co-Owners Should Know
How co-ownership is structured can produce dramatically different tax results when one owner dies. Property acquired from a decedent generally receives a new tax basis equal to its fair market value at the date of death.4Office of the Law Revision Counsel. 26 USC 1014 – Basis of Property Acquired From a Decedent For joint tenancy between non-spouses, only the deceased owner’s share gets this stepped-up basis. If you and a friend each own 50% as joint tenants and your friend dies, only their half receives the new basis. Your half keeps its original basis. Community property gets a much better deal: when one spouse dies, the entire property, both halves, can receive a stepped-up basis, potentially eliminating a large capital gains tax bill if the survivor later sells.
Adding someone to a property title or selling them a share below fair market value can trigger federal gift tax rules. For 2026, you can give up to $19,000 per recipient per year without owing gift tax or filing a return.5Internal Revenue Service. Frequently Asked Questions on Gift Taxes Married couples who elect gift-splitting can combine their exclusions to give up to $38,000 per recipient.6Internal Revenue Service. Rev. Proc. 2025-32 Transfers exceeding these thresholds require a gift tax return (Form 709), and the excess reduces your lifetime estate and gift tax exemption.
Each co-owner reports their proportionate share of rental income on their individual tax return. Married couples who jointly own rental property are generally treated as a partnership for federal tax purposes, but they can elect to file as a qualified joint venture instead if both spouses materially participate and file a joint return.7Internal Revenue Service. Election for Married Couples Unincorporated Businesses Unmarried co-owners with a rental property may need to file a partnership return (Form 1065), depending on the level of their shared business activity.
Investors who sell real property can defer capital gains tax by reinvesting in like-kind replacement property through a Section 1031 exchange. The replacement property must be identified within 45 days of the sale and acquired within 180 days.8Office of the Law Revision Counsel. 26 USC 1031 – Exchange of Real Property Held for Productive Use or Investment Interests in partnerships and LLCs do not qualify as real property for this purpose, which is why some investment sponsors structure shared ownership as a tenancy in common. A TIC interest counts as direct real property ownership, preserving the tax deferral that would be lost if the same property were held through an entity.