Where are you seeing something that says you cannot use an authorization from an executor on a return for a deceased person? I have never seen anything that tells me that. Have you downloaded/read the relevant guide (Preparing Returns for Deceased Persons - 2019)? Page 6 of the guide bears the following note about a Legal Representative requesting another person to act on their behalf: Note As the legal representative, you may wish to appoint an authorized representative to deal with the CRA for tax matters on your behalf. For more information, go to canada.ca/taxes-representative-authorization. I read that to mean that a "Legal Representative" (executor, Probate Court appointee, etc) is authorized to sign an authorization to represent, just as someone with a Power of Attorney can do to a living person.