There are multiple versions of Form ET706. Be sure to use the version that corresponds to the decedent's date of death.The register of wills probates wills and appoints representatives for decedents who die with or without a will. File Form 706 for the estates of decedents who were either. U.S. citizens or U.S. residents at the time of death. Find common questions and answers about estate taxes, including requirements for filing, selling inherited property and taxable gifts. You must file the person's final income tax return(s). Include all unreported income the person earned up to their date of death. You should also complete and file with the final return a copy of Form 1310, Statement of Person Claiming Refund Due a Deceased Taxpayer. You must file Form ET-706 within nine months after the decedent's date of death, unless you receive an extension of time to file the return.