(a) In general. Section 6166 provides that where the value of an interest in a closely held business, which is included in the gross estate of a decedent who was a citizen or resident of the United States at the time of his death, exceeds either (1) 35 percent of the value of the gross estate, or (2) 50 percent of the taxable estate, the executor may elect to pay part or all of the Federal estate tax in installments. The election to pay the tax in installments applies to deficiencies in tax as well as to the tax shown on the return, unless the deficiency is due to negligence, to intentional disregard of rules and regulations, or to fraud with intent to evade tax. Except as otherwise provided in section 6166(i) and § 20.6166-4, the provisions of section 6166 and this section apply only if the due date of the return is after September 2, 1958. See § 20.6166-4 for special rules applicable where the decedent died after August 16, 1954, and the due date of the return was on or before September 2, 1958. See also § 20.6075-1 for the due date of the return, and § 20.6166-2 for definition of the term “interest in a closely held business.” Since the election must be made on or before the due date of the return, the provisions of section 6166 will not apply to a deficiency in a case where, for whatever reason, no election was made to pay in installments the tax shown on the return. However, see paragraph (e)(3) of this section concerning a protective election. The general administrative provisions of Subtitle F of the Code are applicable in connection with an election by the executor to pay the estate tax in installments in the same manner in which they are applied in a case where an extension of time under section 6161 is granted for payment of the tax. See paragraph (a) of § 20.6165-1 for provisions requiring the furnishing of security for the payment of the tax in cases where an extension is granted under section 6161.

(b) Limitation on amount of tax payable in installments. The amount of estate tax which the executor may elect to pay in installments is limited to an amount A, which bears the same ratio to B (the gross Federal estate tax, reduced by the credits authorized by sections 2011 through 2014 and any death tax convention) as C (the value of the interest in a closely held business which is included in the gross estate) bears to D (the value of the gross estate). Stated algebraically, the limitation (A) equals:

(c) Number of installments and dates for payment. The executor may elect to pay part or all of the tax (determined after application of the limitation contained in paragraph (b) of this section) in two or more, but not exceeding 10, equal annual installments. The first installment shall be paid on or before the date prescribed by section 6151(a) for payment of the tax (see paragraph (a) of § 20.6151-1), and each succeeding installment shall be paid on or before the date which is one year after the date prescribed for the payment of the preceding installment. See § 20.6166-3 for the circumstances under which the privilege of paying the tax in installments will terminate.

(d) Deficiencies. The amount of a deficiency which may be paid in installments shall not exceed the difference between the amount of tax which the executor elected to pay in installments and the maximum amount of tax (determined under paragraph (b) of this section) which the executor could have elected to pay in installments on the basis of a return which reflects in adjustments which resulted in the deficiency. This amount is then prorated to the installments in which the executor elected to pay the tax. The part of the deficiency prorated to installments not yet due shall be paid at the same time as, and as a part of, such installments. The part of the deficiency prorated to installments already paid or due shall be paid upon notice and demand from the district director. At the time the executor receives such notice and demand he may, of course, prepay the portions of the deficiency which have been prorated to installments not yet due. See paragraph (h) of this section.

(e) Notice of election—(1) Filing of notice. The notice of election to pay the estate tax in installments shall be filed with the district director on or before the due date of the return. However, if the due date of the return is after September 2, 1958, but before November 3, 1958, the election will be considered as timely made if the notice is filed with the district director on or before November 3, 1958. See § 20.6075-1 for the due date of the return.

(2) Form of notice. The notice of election to pay the estate tax in installments may be in the form of a letter addressed to the district director. The executor shall state in the notice the amount of tax which he elects to pay in installments, and the total number of installments (including the installment due 9 months (15 months, in the case of a decedent dying before January 1, 1971) after the date of the decedent's death, in which he elects to pay the tax. The properties in the gross estate which constitute the decedent's interest in a closely held business should be listed in the notice, and identified by the schedule and item number at which they appear on the estate tax return. The notice should set forth the facts which formed the basis for the executor's conclusion that the estate qualifies for the payment of the estate tax in installments.

(3) Protective election. In a case where the estate does not qualify under section 6166(a) on the basis of the values as returned, or where the return shows no tax as due, an election may be made, contingent upon the values as finally determined meeting the percentage requirements set forth in section 6166(a), to pay in installments any portion of the estate tax, including a deficiency, which may be unpaid at the time of such final determination and which does not exceed the limitation provided in section 6166(b). The protective election must be made on or before the due date of the return and should state that it is a protective election. In the absence of a statement in the protective election as to the amount of tax to be paid in installments and the number of installments, the election will be presumed to be made for the maximum amount so payable and for the payment thereof in 10 equal annual installments, the first of which would have been due on the date prescribed in section 6151(a) for payment of the tax. The unpaid portion of the tax which may be paid in installments is prorated to the installments which would have been due if the provisions of section 6166(a) had applied to the tax, if any, shown on the return. The part of the unpaid portion of the tax so prorated to installments the date for payment of which would not have arrived before the deficiency is assessed shall be paid at the time such installments would have been due. The part of the unpaid portion of the tax so prorated to any installment the date for payment of which would have arrived before the deficiency is assessed shall be paid upon receipt of notice and demand from the district director. At the time the executor receives such notice and demand he may, of course, prepay the unpaid portions of the tax which have been prorated to installments not yet due. See paragraph (h) of this section.

(f) Time for paying interest. Under the provisions of section 6601, interest at the annual rate referred to in the regulations under section 6621 shall be paid on the unpaid balance of the estate tax which the executor has elected to pay in installments, and on the unpaid balance of any deficiency prorated to the installments. Interest on such unpaid balance of estate tax shall be paid annually at the same time as, and as a part of, each installment of the tax. Accordingly, interest is computed on the entire unpaid balance for the period from the preceding installment date to the current installment date, and is paid with the current installment. In making such a computation, proper adjustment shall be made for any advance payments made during the period, whether the advance payments are voluntary or are brought about by the operation of section 6166(h)(2). In computing the annual interest payment, the portion of any deficiency which is prorated to installments the date for payment of which has not arrived shall be added to the unpaid balance at the beginning of the annual period during which the assessment of the deficiency occurs. Interest on such portion of the deficiency for the period from the original due date of the tax to the date fixed for the payment of the last installment preceding the date of assessment of a deficiency shall be paid upon notice and demand from the district director. Any extension of time under section 6161(a)(2) (on account of undue hardship to the estate) for payment of an installment will not extend the time for payment of the interest which is due on the installment date.

(g) Extensions of time for payment in hardship cases. The provisions of section 6161, under which extensions of time may be granted for payment of estate tax in cases involving undue hardship, apply to both the portion of the tax which may be paid in installments under section 6166 and the portion of the tax which is not so payable. Therefore, in a case involving undue hardship, the executor may elect under section 6166 to pay in installments the portion of the tax which is attributable to the interest in the closely held business and, in addition, may file an application under section 6161 for an extension of time to pay both the portion of the tax which is not attributable to the interest in the closely held business and such of the installments as are payable within the period of the requested extension. If an executor files a notice of election to pay the tax in installments and thereafter it is determined that the estate does not qualify for the privilege of paying the tax in installments, the executor is not deprived of the right to request an extension under section 6161 of time for payment of the tax to which the purported election applied. See § 20.6161-1 for the circumstances under which a timely filed election to pay the tax in installments will be treated as a timely filed application for an extension of time to pay the tax on account of undue hardship to the estate.

(h) Prepayments. Voluntary prepayment may be made at any time of all, or of any part, of the unpaid portion of the tax (including deficiencies) payable in installments. Voluntary prepayments shall be applied in payment of such installments, installment, or part of an installment as the person making the prepayment shall designate. For purposes of this paragraph, a payment described in paragraph (d) (2) of § 20.6166-3 of tax in an amount not less than the amount of money or other property distributed in a section 303 redemption is considered to be a voluntary prepayment to the extent paid before the date prescribed for payment of the first installment after the redemption or, if paid on the date prescribed for payment of such installment, to the extent it exceeds the amount due on the installment. See paragraph (b)(3) of § 20.6166-3 for the application to be made of the prepayment required by section 6166(h)(2).