In common law, adverse possession is the name given to the process by which title to another's real property is acquired without compensation, by, as the name suggests, holding the property in a manner that conflicts with the true owner's rights for a specified period of time.

The law of adverse possession is entirely statutory, arising out of a statutory limitation period or statute of limitations.

Requirements for adverse possession

Adverse possession requires the actual, visible, hostile, notorious, exclusive, and continuous possession of the property, and some jurisdictions further require the possession to be made under a claim of title or a claim of right.

In simple terms, this means that those attempting to claim the property are occupying it exclusively (keeping out others) and openly as if it were their own. Some jurisdictions permit accidental adverse possession as might occur with a surveying error. Generally, the openly hostile possession must be continuous (although not necessarily constant) without challenge or permission from the lawful owner, for a fixed statutory period in order to acquire title. Where the property is of a type ordinarily only occupied during certain times (such as a summer cottage), the adverse possessor may only need to be in exclusive, open, hostile possession during those successive useful periods.

Effect of adverse possession

An adverse possessor will be committing a trespass on the property that they have taken and the owner of the property could cause them to be evicted by an action in trespass. All common law jurisdictions require that the action of trespass is brought within a specified time. The effect of a failure by the land owner to evict the adverse possessor depends on the jurisdiction.

In some (such as England and Wales), the title of the landowner will be automatically extinguished once the relevant limiation period has passed. This process now only applies to unregistered land.

In other jurisdictions, the adverse possessor acquires merely an equitable title: the land owner being a trustee of the property for them.

Adverse possession only extends to the property adversely possessed. If the original owner had a title to a greater area (or volume) of property, the adverse possessor does not obtain all of it.

In some jurisdicitons, someone who has successfully obtained title to property by adverse possession may bring an action in land court to "quiet title" of record in their names on some or all of the former owner's property.

Adverse possession does not typically work against property owned by a government agency.

Where land is registered under a Torrens title registration system or similar, special rules apply. It may be that the land cannot be affected by adverse possession (as was the case in England and Wales from 1875 to 1926), or that special rules apply.