Before the year 1990, it was legally required that a third party (witness) be present for the signing of a tenancy agreement. After this period, it was no longer legally required to do so except if the assured shorthold tenancy agreement is for a period of more than 3 years. This is because it is drafted as a deed if the duration is 3 years or more.
However, it is important for a third party to witness and sign an agreement, such as an AST, in order to provide a layer of security for both the landlord and the tenant. A party might deny signing the agreement; stating that they were coerced into signing it or that the signatures were forged. But certain other situations make having a witness particularly advisable. One of these is if the landlord is renting at a price different from the market value. This usually occurs when the tenant is a relative or a close friend.
Most agreements have only two spaces for signatures – the tenant‘s and the landlord‘s. So, there is no place for the witness to sign their name. Merely being present is acceptable, provided the witness can be reached in the future if needed. But the entire idea is usually dealt with by using agreements that are signed electronically, which is the recent norm. This solves the same problem it creates because electronic signatures can be secured with biometrics. This way, they become more protective of both parties than with written agreements whose witness might not be traceable afterwards since they don’t sign.
A simple answer to the present question is that an assured shorthold tenancy agreement does not require a witness, especially if the length of the tenancy is below three years. However, having the signing of the document witnessed does not only offer both parties more protection, but also gives the agreement a more professional look. That helps both parties realize the level of commitment that comes with this document and that the full strength of the law will go against any party that violates the terms. Also, it strengthens the relationship between both parties.