My condolences on the loss of your sister.
A personal representative (fiduciary) is responsible for filing certain tax returns for a person who has died, and for the decedent's estate. The personal representative may be required to file the final income tax return and any returns not filed for preceding years. They also may have to file the income tax return for the estate, and the estate tax return. If no personal representative has been appointed and there is no surviving spouse, the person in charge of the decedent's property must file and sign the return as "personal representative."
You can obtain a transcript of a prior year by calling(NNN) NNN-NNNNand following the prompts in the recorded message or by completing and mailing Form 4506-T, Request for Transcript of Tax Return, to the address listed in the instructions. Forms can be downloaded at www.irs.gov or ordered by calling(NNN) NNN-NNNN You can request any copies as the fuduciary. If there are no copies for certain years then you will know she did not file.
If you're more comfortable talking with someone in person, visit your local Taxpayer Assistance Center where you can spread out your records and talk with an IRS representative face-to-face. No appointment is necessary. You can find your local office by using the following link:
I help this information is helpful,