Frequently, it is revoked by preparing a new Durable Power of Attorney (DPOA), specifically revoking all prior DPOAs. It is still a good idea to specifically communicate the revocation to your former agent and anyone else who may have received a copy of the original DPOA.
It depends a bit on the circumstances. If the POA is not yet effective and you have all the copies, then creating a new POA and tearing up the old copies is sufficient. If there are copies scattered around, then you need to be more diligent about notifying people of the changes.
If the POA is in effect, then you need to send a letter to the agent and anyone the agent has been dealing with, letting them know that the POA has been revoked. The agent is not authorized to act, once notified of the revocation. In order to make sure you are covered, a new POA should be executed, as soon as possible.
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