(a) Generally. Any tax imposed by the Inheritance Tax Law which becomes delinquent (see Section 14103) will bear interest from the delinquent date to the date the tax plus accrued interest is paid in full. Except as provided in Revenue and Taxation Code Section 14212 (see Section 14212), there is no relief from accrued interest for a late payment of the inheritance tax.

(b) Interest Rate on Delinquent Tax Paid in Installments. Any tax imposed by the Inheritance Tax Law which becomes delinquent and is being paid in installments shall bear interest as follows:

(c) Interest Rate on or after January 1, 1976. In all other cases, any tax imposed by the Inheritance Tax Law which has become delinquent prior to and remains unpaid or becomes delinquent on or after January 1, 1976, will bear interest at the rate of 12 percent per annum.

(d) Interest Rate on or after September 22, 1951. Any tax imposed by the Inheritance Tax Law which became delinquent (see Section 14103) on or after September 22, 1951, will bear interest from the delinquent date to the date of payment at the rate of 6 percent per annum. If the tax remains unpaid on January 1, 1976, the interest rate becomes 12 percent per annum from said date to date of payment.

(e) Interest Rate Prior to September 22, 1951. Any tax imposed by the Inheritance Tax Law which became delinquent (see Section 14103) prior to September 22, 1951 (the effective date of the amendment of Revenue and Taxation Code Section 14211 and of the repeal of Revenue and Taxation Code Section 14212), will ordinarily bear interest at the rate of 10 percent per annum from the date of death of the transferor. However, if in the judgment of the court having jurisdiction to determine the tax (see Sections 14651, 14653 and 14653.1) the tax cannot or could not be paid on or before the delinquent date because of pending claims or necessary litigation involving the transferor's estate, or for any other unavoidable cause of delay, it may enter an order reducing the penalty. In such event, the tax will bear interest at 7 percent per annum from the delinquent date (see Section 14103) to the date of payment or to September 22, 1951, whichever is earlier, and in the latter case, at 6 percent per annum from September 22, 1951, to the date of payment (12 percent per annum on unpaid amounts on and after January 1, 1976); provided, that if the cause of delay is removed prior to the payment of the tax and prior to September 22, 1951, the tax will bear interest at 10 percent per annum from the date of such removal to the date of payment or to September 22, 1951, whichever is earlier, and in the latter case, at 6 percent per annum from September 22, 1951, to the date of payment (12 percent on unpaid amounts on and after January 1, 1976). “Necessary litigation” does not include any litigation to defeat the payment of any tax imposed by the Inheritance Tax Law. If no order reducing penalty is obtained, the tax will bear interest at 10 percent per annum from the date of death to the date of payment or to September 22, 1951, whichever is earlier, and in the latter case, at 6 percent per annum from September 22, 1951, to the date of payment (12 percent per annum on unpaid amounts on and after January 1, 1976).

(f) Additional Tax, Different Delinquent Date. An inheritance tax and an additional tax under Revenue and Taxation Code Section 13441 or 13442 imposed by the Inheritance Tax Law in respect to transfers by a decedent may have different delinquent dates (see Section 14103) and, accordingly, may bear interest from different dates. As to both the inheritance tax and the additional tax under Revenue and Taxation Code Section 13441 or 13442 the delinquent date is the same in respect to transfers of decedents whose deaths occur on or after 6:00 p.m., December 8, 1971 (see Section 14103), and interest thereon at 6 percent per annum from nine months after date is applicable to December 31, 1975, and at 12 percent per annum on unpaid amounts thereafter.