When you are doing tax returns or filing jointly with a deceased person, it can be confusing and the IRS just guides you to some random publications.
Here are the easy instructions, with information taken from the IRS’ own Publication 559:
On the First Page of the Tax Return:
1) Write the word “DECEASED,” the decedent’s name, and the date of death across the top of the tax return.
2) If filing a joint return, write the
name and address of the decedent and the surviving spouse in the name and address fields.
3) If a joint return is not being filed, write the decedent’s name in the name field and the personal representative’s name and address in the address field.
On the Second Page of the Tax Return:
1) If a personal representative has been appointed, that person must sign the re-
2) If it is a joint return, the surviving spouse must also sign it.
3) If no personal representative has been appointed, the surviving spouse (on a joint return) signs the return and writes in the signature area “Filing as surviving spouse.”
4) If no personal representative has been appointed and if there is no surviving spouse, the person in charge of the decedent’s property must file and sign the return as “personal representative.”
Since the most people searching this topic are surviving spouses without a personal representative, You need to do step 1 on first page and steps 2 and 3 on the second page.