Interest

(1) Any tax due under this article which is not paid within nine months after the date of the decedent's death or the generation-skipping transfer shall bear interest on the unpaid balance due at the rate prescribed by section 39-21-110.5 from nine months after such death or transfer until such tax is paid. The interest imposed by this section shall apply regardless of any extension of time to pay the tax or of any election to use an installment method of payment of the tax.

(2) If a special use valuation election was made in a federal return and thereafter additional Colorado estate tax is due as a result of a premature disposition of property or premature cessation of the qualified use, interest shall accrue from the due date of the federal additional estate tax return regardless of any federal extension of time for payment.

(3) If a qualified family-owned business deduction election was made in a federal return and thereafter additional Colorado estate tax is due as a result of failure to materially participate in the business, disposition of interests, or other noncompliance with the requirements of section 2057 of the internal revenue code, interest shall accrue from the due date of the federal additional estate tax return regardless of any federal extension of time for payment.

(4) If a qualified conservation easement election was made on a federal return and thereafter additional Colorado estate tax is due as a result of any failure to implement the agreement described in section 2031 of the internal revenue code, interest shall accrue from the due date of the federal additional estate tax return regardless of any federal extension of time for payment.