Sorry for your loss. if he used Turbotax, you would need to know his username and password to accesss the account which would provide info on whether he filed or not. If you don't know his user info you can contact support. However, I do not know if they would provide it. Security concerns.
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you can call the IRS 800-829-1040 but you might need some 2022 or 2023 information so the iRS can verfiy your identity
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you can register with ID.me and then check to see if there is a return transcript
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you can file form 4506-T (free) to get a transcript of the return or 4506 to get a copy for a fee.
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the last two would return nothing or a blank piece of paper if the return was not filed.
. https://www.irs.gov/pub/irs-pdf/f4506.pdf 4506
https://www.irs.gov/pub/irs-pdf/f4506t.pdf 4506-t
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.