you'll need to contact each institution directly with your executor paperwork - death certificate, will, court documents if required - and they'll walk you through their process for transferring accounts to the estate. most banks and investment firms have dedicated probate departments that handle this without needing the original passwords; they verify your authority as executor and then either freeze the account or give you temporary access. don't try guessing passwords or using password recovery tools yourself, since that can create legal headaches. if he had a safe deposit box, check there for account statements or a list of where his money was kept, since tracking down every account can be the hardest part.