1. In a case not involving a false or fraudulent return or failure to file a return, if the Department determines at any time after the tax is due, but not later than 4 years after the return is filed unless a longer period is provided by federal law, that the tax disclosed in any return required to be filed by NRS 375A.015 to 375A.345, inclusive, is less than the tax disclosed by its examination, a deficiency must be determined. That determination may also be made within such time after the expiration of the period as may be agreed upon in writing between the Department and the personal representative.
2. For purposes of this section, a return filed before the last day prescribed by law for filing that return must be considered as filed on that last day.