Filed a 2021 amended returns for a new client where the previous preparer placed several IRA distributions in the 2021 1041 Bypass Trust return (1st year of Bypass Trust) instead of client personal returns.  E-filed amended both 1040 and 1041 returns August 2023 (personal not processed yet as IRS is at least 6mo behind on amended returns).  Taxpayer has just received a CP2000 that the original personal return missed a rather large pension distribution.  CP2000 is using the original filed numbers to start as amended return has yet to be processed.

Problem is, taxpayer is now incapacitated and her son has general POA over her affairs.  What documentation do I need to provide with the 2848 of her son's POA to get authority to speak and how should the 2848 be signed.  Thanks in advance everyone!