One joint tenant might leave the property without ending the tenancy first. A tenancy is a contractual agreement and does not end when a tenant moves out. The tenant who leaves the property stays on the tenancy, is liable for the rent, and can move back in.
As both tenants are jointly and severally liable, the remaining tenant is liable for the full rent.
One joint tenant cannot exclude the other from the property without a court order. Each tenant has the right to occupy the entire property until the tenancy ends, or until the tenancy is transferred.
If either tenant give notice on the tenancy then the tenancy will end within one month.
A new tenancy can then be created (subject to the landlord agreeing) and yourself passing all the criteria (including your guarantor).
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