A: I'll answer this question in two parts: Joint Tenancy and Tenancy in Common.
Jus Accrescendi (the right of survivorship) is the most important difference between a Joint Tenancy (JT) and a Tenancy in Common (TC). Survivorship means that when a Joint Tenant dies, his/her heirs have no claim in the property because the property is left for the surviving joint tenants ONLY. This is because of the Four Unities concept that is essential to show interests in land.
The Four Unities:
Time - Interest of each co-owner must be acquired at the SAME time.
Interest - Each co-owner must plan to have interest for the same extent, nature and duration.
Title - Each co-owner must have derived ownership from the same document... ONE deed.
Possession - The land must not be divided. Each co-owner must be equally entitled to the whole of the property.
If the Four Unities are not all present, the interest cannot be held as joint tenants, but may be held as tenants in common, provided that there is unity of possession.
Severing a Joint Tenancy
In Trinidad and Tobago a Joint Tenancy can be severed (ended) in three ways, identified by Page-Wood V-C in Williams v Hensman (1861) 1 John & H. 546, 557-558; 70 ER at p. 867. It must be a present -not future- intention to sever.
1. Acting upon one’s share (alienation) -
This method involves destroying one of the four unities: possession, interest, title or time. The standard way to do so was unilaterally to assign one’s interest to trustees, or to sell or mortgage one’s interest.
2. A joint tenancy may be severed by mutual agreement by all co-owners.
3. There may be a severance by any course of dealing sufficient to intimate that the interests of all were mutually treated as constituting a tenancy in common.