Mass. Gen. Laws ch. 65 § 22
On or before the date when the tax imposed by this chapter is required to be paid, the executor, administrator, trustee or other person liable to taxation under this chapter shall file with the commissioner a return, in such form as the commissioner, with the approval of the commission, prescribes, giving such information as the commissioner requires for the determination of the tax imposed by this chapter. Where and to the extent applicable, such return shall include a full and complete inventory of all property in which the decedent had an interest taxable under this chapter together with the fair market value thereof on the date of death of the decedent, an attested copy of the will, if any, and a copy of the Federal estate tax return, if any, and a computation of the tax due under this chapter. If an election is made to itemize deductions rather than take the standard deduction as provided in section twenty-seven, a list of debts, expenses of administration and federal estate taxes claimed as deductions shall be included in the return. Any unpaid amount of the tax shown to be due on said return, together with a filing fee as determined annually by the commissioner of administration under the provision of section three B of chapter seven, shall be paid in full with the return. The commissioner may, in his discretion, waive the filing of an inventory or any other portion of the return required by this section which he obtains from the probate court or any other source.
In the event that a federal estate tax return is required to be filed by the estate of the decedent, the executor, administrator, trustee or other person liable to taxation under this chapter shall also file with the commissioner a supplement to the return, in such form as the commissioner, with the approval of the commission, prescribes, reporting the adjustments, if any, made by the federal government in the federal estate tax return and a revised computation of the tax due under this chapter as a result of such adjustments. Such supplement, together with a copy of the final determination of federal estate tax liability, shall be filed and any additional tax due as a result thereof shall be paid within sixty days after the date of the final determination of federal estate tax liability.
Where good cause exists, the commissioner may grant a reasonable extension of time, not exceeding six months or such further time as may be granted by the federal government for the filing of the federal estate return, for filing any return under this chapter. Any such extension shall be granted only if application therefor is made prior to the date when the tax imposed by this chapter is required to be paid and an amount equal to the tax reasonably estimated to be due is paid on or before said date. Failure to pay eighty per cent of the tax due on or before said date shall void any extension of time and the return shall be subject to penalty as a late return. Any such penalty may be abated by the commission, in whole or in part, for good and sufficient cause.
Mass. Gen. Laws ch. 65, § 22