Yes, it is possible for someone to sign a deed of sale in a representative capacity on behalf of another person or entity. This is commonly referred to as signing as an agent or a representative. However, it is important to ensure that the agent has the necessary legal authority to act on behalf of the principal. The authority can be granted by way of a power of attorney, resolution or any other legal document that authorises the agent to act on behalf of the principal. It is recommended that parties seek legal advice before signing any documents as a representative.