"Letters of Office" is not really a letter. Some will, some won't, but every bank should accept a filed small estate affidavit.Begin the probate process. A small estate affidavit is a sworn legal document a person can use to assert a claim to assets from the estate of someone who has died. Opening an Estate Checking Account. You should open a checking account in the name of the estate. No letters of office are now outstanding on the decedent's estate, and no petition for letters is contemplated or pending in Illinois or in any other. Make the process of opening an estate account simple and straightforward with this stepbystep guide. After you sign it in the presence of a notary, you then take it to the bank with a certified death certificate. Customer. Continue following the instructions on the website to fill out the complete EIN application.