My mother in law who died on November 27, 2016 and lived in Arizona has an estate of approximately $500,000, do I have to also file an estate tax return?

[pdeprosperis]

How do I determine if I need to file a form 1041 or a 1040?

[ScruffyCurmudgeon]

@pdeprosperis see reply

[ScruffyCurmudgeon]

The requirement to file a Federal Form 706 Estate Tax return starts with an estate having $5.45 million or more, so no Federal requirement.

Arizona has neither Estate Tax or Inheritance Tax.

You did not provide any other details so it is not clear if you need to file an annual Federal Form 1041 Estate Income Tax return - similar to Form 1040 but for a Decedent's Estate.

[ScruffyCurmudgeon]

Clearly, a Form 1040 must be filed to report all income that was received and all deductible expenses that were paid prior to her death in November.  

Correspondingly, a Form 1041 would have to be filed if income was received in her name or in the name of her estate totalling $600 or more.  All such income and expenses received after her death, that is income in her name and expenses paid out of her assets are reported on the Form 1041. If that will be necessary and if you will have questions about that, write back.

The difficult part is that you will need to apportion any income that was reported on Forms 1099 such as interest or dividends between those two periods.