(1) The department is charged with the administration and enforcement of this article and may promulgate such rules and regulations under the "State Administrative Procedure Act", article 4 of title 24, C.R.S., as may be required to effectuate the purposes of this article.

(2) The department is authorized to collect the tax provided for in this article, including applicable interest and penalties, and shall represent this state in all matters pertaining to the same, either before courts or in any other manner. The department may institute proceedings for the collection of this tax and any interest and penalties on the tax under the provisions of sections 24-4-106 and 24-35-109, C.R.S., or any other applicable law, in the probate court of Denver or in any other court of competent jurisdiction. The mailing of a notice of final agency action shall be considered a final agency action or a final order of such an agency for the purposes of judicial review under section 24-4-106, C.R.S., and such action or order shall become effective sixty days after the mailing of said notice. No distraint and sale proceedings under the provisions of section 24-35-109, C.R.S., shall be commenced until such final agency action or final order of such agency is no longer subject to judicial review under the provisions of section 24-4-106, C.R.S.

(3) Nothing in this article shall be construed to deny the right of appellate review as provided by law and the Colorado appellate rules.

(4)

(a) As used in this subsection (4) and subsections (5) and (6) of this section, the term "tax" includes penalty.

(b) Except as otherwise provided in paragraphs (c) to (e) of this subsection (4) and subsection (6) of this section, the assessment of any tax imposed by this article shall be made within the later of either:

(I) Three years after the filing of the applicable Colorado return; or

(II) One year after the expiration of the period of time provided under the internal revenue code, together with any extensions and suspensions of such period under such code, for assessing a deficiency in the corresponding federal tax or changing the reported federal gross estate or generation-skipping transfer.

(c) Where, before the expiration of the period of limitations on assessment, both the department and the person required to file have consented in writing to an assessment after such time, the tax may be assessed at any time prior to the expiration of the period agreed upon. The period so agreed upon may be extended by subsequent agreements in writing made before the expiration of the period previously agreed upon.

(d) A written proposed adjustment by the department of any tax liability under this article sent to the person required to pay the tax or the representative of such person before the expiration of the period of limitation on assessment under this subsection (4) shall extend such period with respect to such proposed adjustment for one year after a final determination, with respect to such proposed adjustment, or assessment is made.

(e) In the event that a federal amended return is filed, the running of the period of limitations on assessment under this subsection (4) shall be suspended with respect to any additional tax due under this article by reason of such amended return until the date that an amended Colorado return with a true copy of such amended federal return is filed with the department of revenue as required by section 39-23.5-111 (1). In the event that a final determination of federal tax due is made, the running of the period of limitations on assessment under this subsection (4) shall be suspended with respect to any additional tax due under this article by reason of such determination until written notice of such determination, in the form required by regulation, is given to the department as required by subsection (2) of this section.

(f) For the purposes of this subsection (4) and section 39-23.5-112, a tax return filed before the last day prescribed by law or by regulation promulgated pursuant to law for the filing thereof shall be considered as filed on such last day.

(5)

(a) Except as provided in paragraph (b) of this subsection (5) and subsection (6) of this section, an assessment of any tax imposed under this article having been made according to law shall be good and valid, and collection thereof and interest thereon may be enforced at any time within six years from the date of said assessment.

(b) The running of the period of limitations for collection of any such tax shall be suspended for the period of any extension of time for payment thereof under the provisions of section 39-23.5-108 (2).

(6) In the case of failure to file a return or the filing of a false or fraudulent return with the intent to evade tax, the tax may be assessed and collected at any time.

(7) In the event that the federal tax authorities collect or otherwise receive payment of the gross federal tax with respect to which the federal credit would be allowable but for the failure to pay the amount of such federal credit to the department as tax under this article by the person required to file the return or to provide such authorities with acceptable proof of such payment, the Denver probate court or other court of competent jurisdiction shall, on motion of the department:

(a) Order such person to secure the refund of the amount of tax from the federal tax authorities attributable to such federal credit on the behalf of the department in payment of the tax under this article; or

(b) Appoint any qualified person or the department as special administrator for the purpose of securing such refund on behalf of the department in payment of the tax under this article.