Hi Nathalie,
Guarantors will be asked to sign the same tenancy agreement as the tenants, and so become legally liable to cover the rent and/or the cost of damage to the property if the tenant fails to do so.
Most tenancies in the UK are created as Joint Tenancies (whereby several parties are named on one agreement) and it is important to note that this will mean that all parties are jointly liable for all the obligations named in the agreement. In plain English that means that any one tenant or guarantor can be asked to pay the full amount owed by any or all of the other people named on the agreement, should it come to it. Therefore we need to include them in the communication regarding the tenancy.
You can find further information on this topic here:https://www.openrent.co.uk/blog/joint-and-severally-liable-tenancies-a-guide-for-landlords-tenants-and-guarantors/
Kind regards,
Matthew C.