Sign a revocation
A POA is usually cancelled through a notarized revocation that identifies the original document. This creates a clear record that the authority has ended.
Inform the people involved
Let your former attorney know, and notify the banks, authorities or companies that relied on the POA. This helps prevent the old document from being used.
Issue a new POA if needed
If you still need someone to act for you, you can grant a new POA to a different person or with updated powers.