Hi there. From the information you provided, the exact nature of your legal issue is not clear. This means we are unable to specifically address your concern. However, below is some general legal information that may be relevant to your situation.

Disputes between tenants of a rental property can be problematic. While disputes between landlords and tenants are heavily regulated, there are very few laws that specifically deal with disputes between tenants. As general advice, it is recommended that you keep communicating with your co-tenants at all times (especially if there are disagreements) and keep a written record of all important conversations and events.

You said that a co-tenant signed a statutory declaration. This is a written statement made by a person about something they declare to be true. A statutory declaration must be in a special form and signed in front of a qualified witness. If a person has made a false declaration, they may be charged with an offence or liable for perjury. However, these penalties are ordinarily only enforced against declarants by courts or government agencies, not private individuals.

You also referred to a personal agreement with a co-tenant. An agreement or contract can be made between two or more people about a specific transaction or arrangement. It can be oral or written. For an agreement to be legally binding it must meet certain legal requirements. One requirement is that the parties intended to create a legal contract, such that they may sue (or be sued) if someone does not hold up their end of the bargain. Whether the parties intended to create a legal contract will depend on the circumstances in which the agreement was made. This can be difficult to prove. Moreover, even if the contract was legally binding, it can be difficult to enforce between private individuals if it was not put in writing.