California Revenue and Taxation Code
The personal representative of every estate subject to the tax imposed by this part who is required to file a federal estate tax return shall file with the Controller on or before the federal estate tax return is required to be filed both of the following:
(a) A return for the tax due under this part.
(b) A true copy of the federal estate tax return.
If the personal representative has obtained an extension of time for filing the federal estate tax return, the filing required by Section 13501 shall be similarly extended until the end of the time period granted in the extension of time for the federal estate tax return. A true copy of the federal extension shall be filed with the Controller.
If the personal representative files an amended federal estate tax return, he or she shall immediately file with the Controller an amended return with a true copy of the amended federal estate tax return. If the personal representative is required to pay an additional tax under this part pursuant to the amended return, he or she shall pay that additional tax, together with any interest as provided in Section 13550 at the same time the amended return is filed.
Upon final determination of the federal estate tax due, the personal representative shall, within 60 days after that determination, give written notice of it to the Controller. If any additional tax is due under this part by reason of this determination, the personal representative shall pay the same, together with interest as provided in Section 13550, at the same time he or she files the notice.