If you share a rented property with a partner, friend, or housemate, you may have a joint tenancy. This means each of you is individually liable for the entire rent, not just your share. If one joint tenant stops paying, the landlord can pursue any or all of the remaining tenants for the full amount. This is called "joint and several liability".
Joint tenants also share responsibility for the condition of the property and any obligations in the tenancy agreement. If a deposit dispute arises, it involves all named tenants, even if only one person caused the damage in question.
Under the Renters' Rights Act, a joint periodic tenancy can be ended by any one of the joint tenants giving two months' notice. This means that if one person decides to leave, the tenancy ends for everyone unless the remaining tenants negotiate a new tenancy with the landlord. This can create difficulties in shared housing situations, so it's worth discussing with your housemates before anyone serves notice.