On the internet at https://www.irs.gov/businesses/small-businesses-self-employed/deceased-taxpayers-filing-the-final-re... it states “In general, the final individual income tax return of a decedent is prepared and filed in the same manner as when they were alive.”
So now you have to look at the IRS from 1040 instructions https://www.irs.gov/pub/irs-pdf/f1040.pdf
in the section "So I Have To File." There you will find that a single person under 65, has to file if they earn 12,500 or more. Of course if they had tax withheld you must file to get any refund due.
There are also other special credits that are listed that require filing in order to obtain those credits. See the Instructions.
