A concurrent estate or co-tenancy is a concept in property law, particularly derived from the common law of real property, which describes the various ways in which property can be owned by more than one person at a given time. The parties who own property jointly are referred to as co-tenants or joint tenants. Most common-law jurisdictions recognize three kinds of concurrent estate: tenancy in common, joint tenancy with right of survivorship, and tenancy by the entirety. Many jurisdictions simply refer to a joint tenancy with right of survivorship as a joint tenancy, but a few U.S. States treat the phrase joint tenancy as synonymous with a tenancy in common.

Rights and duties shared by all cotenants

Co-tenants, irrespective of the type of tenancy, share certain rights to the property:

1. Each tenant has an unrestricted right of access to the property. Where one co-tenant wrongfully excludes another from making use of the property, the excluded co-tenant can bring a cause of action for ouster, and may receive the fair rental value of the property for the time that he was dispossessed.
2. Each tenant has a right to an accounting of profits made from the property. If the property generates income such as rent, each tenant is entitled to a proportion of that income.
3. Each tenant has a right of contribution for the costs of owning the property. Co-tenants can be forced to contribute to the payment of expenses such as repairs, property taxes, and mortgages on the entire property.

Co-tenants have no obligation to contribute to any costs of improving the property. Furthermore, each co-tenant can independently encumber their own share in the property by taking out a mortgage on that share; other co-tenants have no obligation to help pay a mortgage that only runs to another tenant's share of the property, and the mortgagee can only foreclose on that share.

Finally, co-tenants owe one another a duty of fair dealing. Because of this, any co-tenant who acquires a mortgage claim against the property must give his co-tenants a reasonable opportunity to purchase proportionate shares in that claim.

Destruction of a tenancy in common

Where the parties to a tenancy in common wish to destroy the joint interest, they can do so through a partition of the property - a division of the land into distinctly owned plots.

If the parties are unable to agree to a partition, any or all of them may seek the ruling of a court to determine how the land should be divided up, physically divide it between the joint owners, leaving each with ownership of a portion of the property representing their share.