So sorry for your loss. You mention "ex-husband" but do not mention when you divorced. If you were divorced before the end of 2023, then you could not have filed a joint tax return, or even married filing separately. Each of you could only file as Single or if one of you had custody of the children, Head of Household.
If you were still married for all of 2023, check your IRS account online to see if a tax return was filed for your SSN.
https://www.irs.gov/payments/your-online-account
You say he passed away "this year"----do you mean he passed in 2024 or in 2025? Again---you have not mentioned when you divorced, so it is difficult to help you. Please post back with details so we will know how to help. But do not post any personal information like names, emails or SSN's.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
