Where more than 10 years after the death of the decedent, beneficiaries of the estate discovered additional assets in the Comptroller's Unclaimed Property records, the estate was not required to file an amended estate tax return. Advisory Opinion, TSB-A-17(1)M (N.Y.S. Dep't of Taxation & Fin., Oct. 6, 2017). The Department concluded that, since the additional assets were not discovered until 10 years after the estate tax return had been filed, the three-year statutory period to assess had passed. The Department further ruled that, even if the unclaimed property had been discovered within six years after the original estate tax return had been filed, the extended six-year period applicable to amounts omitted from the estate tax return that are in excess of 25% of the total estate would not have applied, because the omitted amount did not meet the 25% threshhold.