An enduring power of attorney continues to operate if a donor becomes legally incapacitated. A general power of attorney will cease automatically in this situation.

Sometimes it is difficult to assess whether or not someone is legally incapacitated. Legally incapacitated means that someone is unable to understand the nature of the document and its effect, or is unable to communicate in any way. If there is a question about a person's competence it is best to obtain a written medical opinion, and it is best to get that from the person's own doctor.

Being physically incapacitated, for example being paralysed and being unable to sign documents, does not mean that person is necessarily legally incapacitated. The person may still be able to understand the document and its implications. To have legal capacity, the person needs to be able to communicate in some way. This can be a complex area of law. Legal advice should be sought if there is any question as to a person's legal capacity.

It is not possible to make an enduring power of attorney after a donor has already become legally incapacitated. The affairs of a person who no longer has legal capacity and has not made an enduring power of attorney may still be handled on an informal basis in some cases - for example, if the person's money is in a joint bank account with only one person needing to sign. If complicated matters or family disputes arise, anyone with a proper interest in the care of the person can make an application to the South Australian Civil and Administrative Tribunal (SACAT) to appoint an administrator to manage the person's financial affairs. The Tribunal can appoint an administrator for a person it considers to be incapable of being in control of his or her own affairs, see Guardianship and Administration.