How Do I Sign Legal Documents Under a Power of Attorney?

My friend "Jane" has a power of attorney (POA) for her elderly uncle. Since he is unable to make any legal decisions on his own, she has the capacity to handle all his affairs, including making decisions in regards to his medical matters. There are no limitations. She has complete control over her uncle's affairs. Still, Jane often gets questioned when she signs a legal document for her uncle. She carries a copy of the POA with her to prove she has the legal right. She wondered if it's because the grantor of the power of attorney is her uncle, and not her parent. Then she wondered if the way she signs for him raises a red flag. The attorney instructed her to sign simply "Jane Doe, POA". Read this informative article and find out the answer to the question, "How Do I Sign Legal Documents Under A Power of Attorney?"

How Do I Sign Legal Documents Under A Power of Attorney?

What Standardlegal.com says...
According to Standardlegal.com, you should simply sign your name with "Power of Attorney" behind it. This is sufficient. The website goes on to state that you should never, ever sign the grantor's name, only your own. Standardlegal.com also recommends that, when you are acting as an "Attorney in Fact", you should provide a copy of the power of attorney "whenever a contract or agreement is substantial".

What the American Bar Association Section of Real Property, Trust and Estate Law says...
On the other hand, the American Bar Association- the authoritative resource I would go with- says that agents for grantors should sign legal documents one of two ways. Either "John Doe, by Jane Doe under POA". Or, "Jane Doe, attorney-in-fact for John Doe".

And, the ABA says that you as the agent often "must present the actual document to invoke the power." The exception is in signing checks. You shouldn't need to show your power of attorney when you sign checks on behalf of the grantor.

Jane says that certain businesses she deals with repeatedly on behalf of her uncle ask for a copy of the power of attorney to keep on file. That way, she doesn't need to repeatedly show it to them.

Conclusion
I don't know if the method you choose (of the ones discussed above) to sign legal documents really makes a difference. I do know that you need to carry the power of attorney with you so you can prove that you have the legal right to sign for a grantor.

Resources
http://www.standardlegal.com/blog/if-i-have-power-of-attorney-how-do-i-sign-legal-documents-on-behalf-of-my-grantor/

http://www.abanet.org/rppt/public/power-of-atty.html