A power of attorney is a document granting an agent the legal right to perform legal acts on behalf of the person who granted the power of attorney, known as the principal. You can grant most of your legal rights to an agent, including the right to perform financial transactions, such as cashing a Social Security check.
A power of attorney should include both your name and your agent's name. It should describe the agent's authority and include the signatures of both you and your agent. If no beginning and ending dates are indicated for the agent's authority, the power of attorney will endure indefinitely from that date that you sign it. Some states impose additional requirements, such as notarization of your signatures or signatures of witnesses. Some states provide standardized power of attorney forms but do not require you to use them.
Your agent is bound by legal fiduciary duties, regardless of whether these duties are stated in the power of attorney itself. The two primary fiduciary duties are the duty of loyalty and the duty of care. The duty of loyalty binds your agent to act on behalf of your interests, not his own. He may not benefit from any transactions he performs on your behalf, even if his benefit doesn't harm you, except that you may provide compensation to your agent in the power of attorney. The duty of care binds your agent to treat your Social Security checks and cash with the same degree of care that he would exercise if they were his own property.
Identify yourself and your agent with enough specificity to ensure that there is no ambiguity. If your agent's name is John Smith, for example, you should include his home address to ensure that he is not confused with another John Smith. Carefully draft the section granting your agent's authority. Don't phrase the grant of authority too generally by giving your agent the right to sign your name on your checks -- limit his authority to Social Security checks. If you want your agent's authority to begin and end on specific dates, list these dates.
You may revoke your agent's authority at any time, regardless of the ending date specified in the power of attorney, as long as you are mentally competent and able to communicate. If you wish to revoke the power of attorney early, do so in writing and require the agent to return to you his copy of the power of attorney. If he is allowed to retain a copy, he can still cash your Social Security checks even after you revoke his authority, simply by showing the bank his old power of attorney. As long as the bank had no reason to know of your revocation, it will not be legally liable for cashing the check, although you could file a lawsuit against your agent.