Section 6075(a) provides that the estate tax return "shall be filed within 9 months after the date of the decedent's death."
Reg. section 20.6075-1 provides that the estate tax return is due 9 months after the date of death and the day in the ninth month must “numerically correspond” to the date of death.
Example: Date of death is Apr-12-2008. The return due date is Jan-12-2009.
Absence of a Numerically Corresponding Day in the Ninth Month
Reg. section 20.6075-1 also provides that “if there is no numerically corresponding day in the ninth month, the last day of the ninth month is the due date.”
Example: Date of death is May 31, 2007. The return due date is February 29, 2008, which is a leap year.
Section 6166 interest payment (and annual installment) due dates would fall on February 28 in non-leap years and on February 29 in leap years. If the estate elected a month other than February for payment of the first installment, then the annual installments would be due on the 30th or 31st of such other month, as the case may be. Notwithstanding an estate's election for payment of the first installment in such other month, however, interest payments for the first 4 years after the return due date would remain due on February 28 in non-leap years or February 29 in leap years.
What Happens When the Return Due Date Falls on a Saturday, Sunday, or Legal Holiday
Code section 7503 provides:
When the last day prescribed under authority of the internal revenue laws for performing any act falls on a Saturday, Sunday, or a legal holiday, the performance of such act shall be considered timely if it is performed on the next succeeding day which is not a Saturday, Sunday, or a legal holiday [emphasis added]. For purposes of this section, the last day for the performance of any act shall be determined by including any authorized extension of time.
NOTE: Section 7503 does not change the statutory due date. It merely provides that the performance of the act required on the due date will be considered timely when performed on the next business day.
Reg. section 20.6075-1 provides:
When the due date falls on a Saturday, Sunday, or a legal holiday, the due date for filing the return is the next succeeding day that is not Saturday, Sunday, or a legal holiday. [Emphasis added.]
There is a fine distinction between the estate tax return due date and the estate tax return filing due date. The distinction between the return due date and the return filing due date relates to the timeliness of filing. It does not relate to the beginning date for computing interest.
Section 6151(a) and Reg section 20.6151-1(a) provide that the date fixed for payment of estate tax is the date fixed for filing the estate tax return, determined without regard to any extension of time for filing the return [emphasis added].
If the original return is filed on the first business day after a due date that falls on a weekend, the Service will not bill the estate for interest for that period unless other factors intervene; e.g., the tax shown due on the return is not paid on the return filing due date, or a deficiency is assessed. When a deficiency or interest on underpaid tax is assessed, interest begins accruing from the return due date even if it falls on a Saturday, Sunday, or legal holiday. Section 6601; Rev. Rul 74-235, 1974-1 CB 347; FSA 200021010. Also see example 1 under Reg. section 301.6601-1(b)(2), where interest on unpaid income tax for 1955 began accruing on Sunday, April 15, 1956, and Brown v. United States, 393 F. 2d 653, US Court of Claims, March 15, 1968 to the same effect.