The four unities is a concept in the common law of

real property In English common law, real property, real estate, immovable property or, solely in the US and Canada, realty, is land which is the property of some person and all structures (also called improvements or fixtures) integrated with or affixe ...

that describes conditions that must exist in order to create certain kinds of property interests. Specifically, these four unities must be met for two or more people to own property as joint tenants with legal right of survivorship, or for a married couple to own property as

tenants by the entirety In property law, a concurrent estate or co-tenancy is any of various ways in which property is owned by more than one person at a time. If more than one person owns the same property, they are commonly referred to as co-owners. Legal terminolo ...

. Some jurisdictions may require additional unities.

The four unities

; Unity of time : Interest must be acquired by both tenants at the same time. ::In common law, the "time" requirement could be satisfied only by using a "

straw man A straw man (sometimes written as strawman) is a form of argument and an informal fallacy of having the impression of refuting an argument, whereas the real subject of the argument was not addressed or refuted, but instead replaced with a false o ...

" to create a joint tenancy. The party creating the joint tenancy would have to convey title to a straw man, who would then transfer title to the two parties as joint tenants. ; Unity of title : The interests held by the co-owners must arise out of the same instrument.''Re Murdoch and Barry'' (1976), 10 O.R. (2d) 626 (H.C.J.). ; Unity of interest : Both tenants must have the same interest in the property. ::This means that the joint tenants must have the same type of interest, and the interest must run for the same duration. For example, if X and Y create a joint tenancy, both X and Y's interests must be in

fee simple absolute In English law, a fee simple or fee simple absolute is an estate in land, a form of freehold ownership. A "fee" is a vested, inheritable, present possessory interest in land. A "fee simple" is real property held without limit of time (i.e., perm ...

. If, for example, X has a fee simple absolute and Y has a

life estate In common law and statutory law, a life estate (or life tenancy) is the ownership of immovable property for the duration of a person's life. In legal terms, it is an estate in real property that ends at death when ownership of the property may r ...

, there is no unity of interest. ; Unity of possession : Both tenants must have the right to possess the whole property. If any of the four unities is broken and it is not a joint tenancy, the ownership reverts to a tenancy in common. The unique aspect of a joint tenancy is that as the joint tenancy owners die, their shares accrue to the surviving owner(s) so that, eventually, the entire share is held by one person.

A fifth unity

; Unity of marriage : For a

tenancy by the entirety In property law, a concurrent estate or co-tenancy is any of various ways in which property is owned by more than one person at a time. If more than one person owns the same property, they are commonly referred to as co-owners. Legal terminolo ...

this fifth unity must be present. Marriage combined with the preceding four unities creates a tenancy by the entirety. A tenancy by the entirety gives rise to certain legal rights, such as rights of survivors, when one spouse is deceased that interest automatically passes to the surviving spouse. Additionally, in many States, the creditor of only one of the spouses cannot take the property held as tenants by the entirety; both spouses must be indebted to the creditor.

A sixth unity

; Unity of unison : For the parties unite, they must be in unison. This has been criticised by the Law Commission in their 283rd report, entitled 'Unity in Leaseholds'.

References

Property law {{law-term-stub