When a person dies, there are several tax returns that might need to be filed.
The first return is the decedent's final individual income tax return (Form 1040).  That return is for the period beginning the start of the year (usually January 1st) and ending on the date of death.
The second return is referred to as the Estate Tax Return (Form 706), and is a tax on the total asset value of the estate upon the decedent's death.  As of 2021, if the decedent lives in Oregon and the estate value is greater than one million dollars, then an Oregon Form 706 has to be filed, and there will be taxes due if the taxable estate is greater than one million dollars.  In Washington, that threshold is two million dollars.  For Federal the threshold is $11,700,000.  This form and the next form become complicated, so you should be using attorneys and tax practitioners for these form preparations.  You can call us at 503.723.4223 for advice.
The third return is referred to as the Fiduciary Tax Return (Form 1041), and is a tax on the income of the estate.  That return is filed for the period from the date of death to the end of the month and not to exceed twelve months from the date of death.  Example:  date of death is August 25, 2021.  Return can go from August 25, 2021 to December 31, 2021 or July 31, 2022.  If the estate is still open after the ending filing date, then an additional, or additional, returns may need to be filed.