What are joint tenants?
Joint tenants own property together in undivided shares. When one owner dies, their interest passes automatically to the survivor by survivorship, regardless of what their will says. The share does not form part of the deceased's estate for distribution.
It is the default for married couples and civil partners, and generally what they want. It also means you cannot leave your share to anyone else — a will attempting to do so simply has no effect on it.
The tenancy can be severed, converting it into a tenancy in common, by written notice to the other owner or by conduct. A Form A restriction is then entered on the title at HM Land Registry.
Severance is worth considering where children from a previous relationship need protecting, where contributions were unequal, or where a life interest trust is planned. The property still counts in the estate for inheritance tax even though it passes outside it for distribution — a distinction that regularly confuses.