My wife passed, & the IRS said I had to fill out Form 1041 also. Go to the IRS web site to download it. It is somewhat confusing, & I suggest ordering the Business TT to do it. However, you may find it simpler to just call the phone # IRS provides for questions re the 1041, at [phone number removed].
It's all part of what is called "Letters of Administration", obtainable through the Registar of Wills. They assign an EIN, which is what the IRS wants you to use with all filings. If you need help in determining your annual accounting year (tax year) my letter says go to www.irs.com and look up Publication538.
Personally I would hire a licensed tax preparer to do it for you. This would save you a lot of research, anxiety, worry, and get it out of the way quickly.
