CO Code § 39-1-104 (2021)
2021 Colorado Code|Title 39 - Taxation|Article 1 - General Provisions|§ 39-1-104. Valuation for Assessment - Definitions

  The valuation for assessment of all taxable property in the state shall be twenty-nine percent of the actual value thereof as determined by the assessor and the administrator in the manner prescribed by law, and such percentage shall be uniformly applied, without exception, to the actual value, so determined, of the real and personal property located within the territorial limits of the authority levying a property tax, and all property taxes shall be levied against the aggregate valuation for assessment resulting from the application of such percentage. This subsection (1) only applies to nonresidential property that is classified as lodging property. (1.5) Repealed. (1.6)   Hotels, motels, bed and breakfasts, and personal property located at a hotel, motel, or bed and breakfast are classified as lodging property, which is a subclass of nonresidential property for purposes of the valuation for assessment. Classification as a lodging property does not affect a partial allocation as residential real property if a lodging property is a mixed-use property.    Real and personal property valued under section 39-4-102 (1)(e) or (1.5) or section 39-5-104.7 is classified as renewable energy production property, which is a subclass of nonresidential property for purposes of the valuation for assessment.    Real and personal agricultural property is a subclass of nonresidential property for purposes of the valuation for assessment. (1.8)   The valuation for assessment of real and personal property that is classified as agricultural property or renewable energy production property is twenty-nine percent of the actual value thereof; except that, for property tax years commencing on January 1, 2022, and January 1, 2023, the valuation for assessment of this property is temporarily reduced to twenty-six and four-tenths percent of the actual value thereof.    The valuation for assessment of all nonresidential property that is not specified in subsection (1) or (1.8)(a) of this section is twenty-nine percent of the actual value thereof.    The actual value of real and personal property specified in subsection (1.8)(a) or (1.8)(b) of this section is determined by the assessor and the administrator in the manner prescribed by law, and a valuation for assessment percentage is uniformly applied, without exception, to the actual value, so determined, of the various classes and subclasses of real and personal property located within the territorial limits of the authority levying a property tax, and all property taxes are levied against the aggregate valuation for assessment resulting from the application of the percentage.    As used in this section, unless the context otherwise requires, “nonresidential property” means all taxable real and personal property in the state other than residential real property, producing mines, or lands or leaseholds producing oil or gas. Nonresidential property includes the subclasses of agricultural property, lodging property, and renewable energy production property for purposes of the ratio of valuation for assessment.          Repealed.    “Valuation for assessment”, as used in this section and in articles 1 to 13 of this title, means the same as the term “assessed valuation” as that term may appear in the laws of this state.    Except as provided in section 39-7-109, nonproducing severed mineral interests are to be valued at twenty-nine percent of actual value in the same manner as other real property specified in subsection (1.8)(b) of this section. Such valuation shall be determined by the assessing officer only upon preponderant evidence shown by such officer that the cost approach, market approach, and income approach result in uniform and just and equal valuation.    to (10.1) Repealed. (10.2)   Except as otherwise provided in subsection (12) of this section, beginning with the property tax year which commences January 1, 1989, a reassessment cycle shall be instituted with each cycle consisting of two full calendar years. At the beginning of each reassessment cycle, the level of value to be used during the reassessment cycle in the determination of actual value of real property in any county of the state as reflected in the abstract of assessment for each year in the reassessment cycle shall advance by two years over what was used in the previous reassessment cycle; except that the level of value to be used for the years 1989 and 1990 shall be the level of value for the period of one and one-half years immediately prior to July 1, 1988; except that, if comparable valuation data is not available from such one-and-one-half-year period to adequately determine the level of value for a class of property, the period of five years immediately prior to July 1, 1988, shall be utilized to determine the level of value. Said level of value shall be adjusted to the final day of the data gathering period.    During the two years of each reassessment cycle, in preparation for implementation in the succeeding reassessment cycle, the respective assessors shall conduct revaluations of all taxable real property utilizing the level of value for the period which will be used to determine actual value in such succeeding reassessment cycle and the manuals and associated data published for the period which will be used to determine actual value in such succeeding reassessment cycle.    Repealed.    For the purposes of this article and article 9 of this title, “level of value” means the actual value of taxable real property as ascertained by the applicable factors enumerated in section 39-1-103 (5) for the one-and-one-half-year period immediately prior to July 1 immediately preceding the assessment date for which the administrator is required by this article to publish manuals and associated data. Beginning with the property tax year commencing January 1, 1999, if comparable valuation data is not available from such one-and-one-half-year period to adequately determine such actual value for a class of property, “level of value” means the actual value of taxable real property as ascertained by said applicable factors for such one-and-one-half-year period, the six-month period immediately preceding such one-and-one-half-year period, and as many preceding six-month periods within the five-year period immediately prior to July 1 immediately preceding the assessment date as are necessary to obtain adequate comparable valuation data. Said level of value shall be adjusted to the final day of the data-gathering period.    Repealed. (10.3) Repealed.     It is the intent of the general assembly, as manifested in subsection (10.2) of this section, that, when a change occurs in reassessment cycles as prescribed in said subsection, new manuals and associated data will be published by the administrator, pursuant to section 39-2-109 (1)(e), and that said manuals and associated data and the level of value for the year that said manuals and associated data are published shall be utilized by assessors in the manner described in subsection (10.2) of this section for determining the actual value of real property in each county of the state. (a) (I)It is the intent of the general assembly, as manifested in subsection (10.2) of this section, that, when a change occurs in reassessment cycles as prescribed in said subsection, new manuals and associated data will be published by the administrator, pursuant to section 39-2-109 (1)(e), and that said manuals and associated data and the level of value for the year that said manuals and associated data are published shall be utilized by assessors in the manner described in subsection (10.2) of this section for determining the actual value of real property in each county of the state.    The general assembly hereby further finds and declares that it is the intent of paragraph (b) of this subsection (11) to comply with the provisions of section 3 of article X of the state constitution, including the provision which requires the enactment of “general laws, which shall prescribe such methods and regulations as shall secure just and equalized valuations for assessments of all real and personal property”; to reduce the confusion of the owners of taxable property within the state concerning assessment procedures and valuations of such property; to achieve valuations for assessment which represent the current value of such property to the extent which is equitably and practically possible; and to minimize the costs associated with achieving such current valuations for assessment.         The provisions of subsection (10.2) of this section are not intended to prevent the assessor from taking into account, in determining actual value for the years which intervene between changes in the level of value, any unusual conditions in or related to any real property which would result in an increase or decrease in actual value. If any real property has not been assessed at its correct level of value, the assessor shall revalue such property for the intervening year so that the actual value of such property will be its correct level of value; however, the assessor shall not revalue such property above or below its correct level of value except as necessary to reflect the increase or decrease in actual value attributable to an unusual condition. For the purposes of this paragraph (b) and except as otherwise provided in this paragraph (b), an unusual condition which could result in an increase or decrease in actual value is limited to the installation of an on-site improvement, the ending of the economic life of an improvement with only salvage value remaining, the addition to or remodeling of a structure, a change of use of the land, the creation of a condominium ownership of real property as recognized in the “Condominium Ownership Act”, article 33 of title 38, C.R.S., any new regulations restricting or increasing the use of the land, or a combination thereof, the installation and operation of surface equipment relating to oil and gas wells on agricultural land, any detrimental acts of nature, and any damage due to accident, vandalism, fire, or explosion. When taking into account such unusual conditions which would increase or decrease the actual value of a property, the assessor must relate such changes to the level of value as if the conditions had existed at that time. (b) (I) The provisions of subsection (10.2) of this section are not intended to prevent the assessor from taking into account, in determining actual value for the years which intervene between changes in the level of value, any unusual conditions in or related to any real property which would result in an increase or decrease in actual value. If any real property has not been assessed at its correct level of value, the assessor shall revalue such property for the intervening year so that the actual value of such property will be its correct level of value; however, the assessor shall not revalue such property above or below its correct level of value except as necessary to reflect the increase or decrease in actual value attributable to an unusual condition. For the purposes of this paragraph (b) and except as otherwise provided in this paragraph (b), an unusual condition which could result in an increase or decrease in actual value is limited to the installation of an on-site improvement, the ending of the economic life of an improvement with only salvage value remaining, the addition to or remodeling of a structure, a change of use of the land, the creation of a condominium ownership of real property as recognized in the “Condominium Ownership Act”, article 33 of title 38, C.R.S., any new regulations restricting or increasing the use of the land, or a combination thereof, the installation and operation of surface equipment relating to oil and gas wells on agricultural land, any detrimental acts of nature, and any damage due to accident, vandalism, fire, or explosion. When taking into account such unusual conditions which would increase or decrease the actual value of a property, the assessor must relate such changes to the level of value as if the conditions had existed at that time.    The creation of a condominium ownership of real property by the conversion of an existing structure shall be taken into account as an unusual condition as provided for in subparagraph (I) of this paragraph (b) by the assessor, when at least fifty-one percent of the condominium units, as defined in section 38-33-103 (1), C.R.S., in a multiunit property subject to condominium ownership have been sold and conveyed to bona fide purchasers and deeds have been recorded therefor.       Repealed. (12.1) Repealed. (12.2)   Except as provided in subsection (12) of this section, for property tax years commencing on or after January 1, 1987, the requirement stated in subsections (10.2) and (11) of this section that the actual value of real property be determined according to a specified year's level of value and manuals and associated data published by the administrator for said specified year pursuant to section 39-2-109 (1)(e) shall apply to the assessment of all classes of real property, including but not limited to the following classes of real property:   (Deleted by amendment,L. 87, p. 1390, § 2, effective April 1, 1987.)    (Deleted by amendment,L. 87, p. 1392, § 2, effective April 1, 1987.)    Operating property and plants of public utilities; and    Agricultural land.    (Deleted by amendment,L. 87, p. 1385, § 1, effective June 20, 1987.)       This subsection (12.2) shall take effect January 1, 1987. (12.3)     The actual value of personal property is determined by appropriate consideration of such of the three approaches specified in section 39-1-103 (5)(a) as are applicable to the appraisal of such property and is based on the property's value in use. Subject to review and approval pursuant to section 39-2-109 (1)(e), the administrator shall prepare and publish appraisal procedures and instructions for the annual appraisal of such property that include a definition of “value in use” and a factor or factors to adjust the actual value for the current year of assessment to the level of value applicable to real property. (a) (I)The actual value of personal property is determined by appropriate consideration of such of the three approaches specified in section 39-1-103 (5)(a) as are applicable to the appraisal of such property and is based on the property's value in use. Subject to review and approval pursuant to section 39-2-109 (1)(e), the administrator shall prepare and publish appraisal procedures and instructions for the annual appraisal of such property that include a definition of “value in use” and a factor or factors to adjust the actual value for the current year of assessment to the level of value applicable to real property.    In determining actual value, depreciation attributable to age shall not exceed that for the actual age of the property on the assessment date. Physical, functional, and economic obsolescence shall be considered in determining actual value.       Repealed. (12.4) For property tax years commencing on and after January 1, 1987, the requirement stated in subsections (10.2) to (11) of this section that the actual value of real property be determined according to a specified year's level of value and manuals and associated data published by the administrator for said specified year pursuant to section 39-2-109 (1)(e) shall not apply to the assessment of producing coal mines and other lands producing nonmetallic minerals.   During each property tax year, the director of research of the legislative council shall contract with a private person for a valuation for assessment study to be conducted as set forth in this subsection (16). The study shall be conducted in all counties of the state to determine whether or not the assessor of each county has, in fact, used all manuals, formulas, and other directives required by law to arrive at the valuation for assessment of each and every class of real and personal property in the county. The person conducting the study shall sample each class of property in a statistically valid manner, and the aggregate of such sampling shall equal at least one percent of all properties in each county of the state. The sampling shall show that the various areas, ages of buildings, economic conditions, and uses of properties have been sampled. Such study shall be completed, and a final report of the findings and conclusions thereof shall be submitted to the state board of equalization, by September 15 of the year in which the study is conducted.    During each property tax year, beginning with the property tax year which commences January 1, 1985, in addition to the requirements set forth in paragraph (a) of this subsection (16), the study shall set forth the aggregate valuation for assessment of each county for the year in which the study is conducted.    The person conducting any valuation for assessment study pursuant to this subsection (16) and his employees shall, during the term of his contract, have access to any document in the custody of the administrator or an assessor, including, but not limited to, such documents as are held pursuant to sections 39-4-103, 39-5-120, and 39-14-102 (1)(c). The penalties in section 39-1-116 apply against the divulging at any time of any confidential information obtained pursuant to this paragraph (c).    Repealed.                    (11)   (12)   (a) For the property tax years commencing on or after January 1, 1987, producing mines shall be valued for assessment solely pursuant to article 6 of this title.   (b) For the property tax years commencing on or after January 1, 1987, oil and gas leaseholds and lands shall be valued for assessment solely pursuant to section 39-7-102 .   (c) Repealed.   (13)Repealed.   (14)Repealed.   (15) Repealed.    (16)   History. Source: L. 64: R&RE, p. 676, § 1. C.R.S. 1963: § 137-1-4. L. 65: P. 1096, § 2. L. 67: P. 946, § 5. L. 70: Pp. 380, 388, §§ 10, 28. L. 73: P. 1430 § 1. L. 75: (5) and (6) added, pp. 863, 1474, §§ 2, 1, effective July 1; (7) added, p. 1454, § 1, effective July 30. L. 76: (9) added, p. 755, § 5, effective July 1; (8) added, p. 755, § 4, effective January 1, 1977. L. 77: (10) R&RE and (11) and (12) added, pp. 1731, 1732, §§ 4, 5, effective June 20. L. 79: (13) added, p. 1329, § 2, effective May 8; (6) R&RE and (14) added, pp. 1403, 1327, §§ 1, 4, effective July 1; (2) amended, p. 1402, § 1, effective January 1, 1980. L. 80: (10) amended, p. 714, § 1, effective February 29; (9) amended, p. 711, § 1, effective April 16. L. 81: (13)(b) amended, p. 1836, § 1, effective June 4; (9)(a), (10)(a), (10)(b), and IP(12) amended, p. 1830, § 2, effective June 12; (12)(c), (12)(d), (12)(g), and (12)(h) amended, pp. 1848, 1854, §§ 4, 2, effective January 1, 1982; (16) added, p. 1397, § 8, effective January 1, 1983. L. 82: (11)(b) amended, p. 553, § 1, effective May 3; (16) amended, p. 457, § 2, effective January 1, 1983. L. 83: (2), (7), and (12.3)(b) repealed and (12.3)(a)(I) and (16) amended, pp. 1485, 1482, §§ 11, 3, effective April 22; (10), (11)(a), (11)(b)(I), and (12)(h) amended and (10.1), (12.1), and (12.2) added, pp. 1494, 1495, §§ 1, 2, effective April 28; (5) repealed, p. 2081, § 1, effective January 1, 1984. L. 84: (15) repealed, p. 999, § 3, effective January 1; (10), (10.1)(a), (12)(h), (12.1), IP(12.2)(a), and (12.2)(b) amended, p. 988, § 1, effective February 23. L. 85: (4) amended, p. 1212, § 8, effective May 9. L. 86: (16)(a) amended, p. 1101, § 1, effective March 26. L. 87: (16)(c) added, p. 1417, § 1, effective March 13; (12)(a) RC&RE and (12.2)(a) amended, p. 1390, §§ 1, 2, effective April 1; (12)(b) RC&RE and (12.2)(a) amended, p. 1392, §§ 1, 2, effective April 1; (1.5) added, p. 1384, § 1, effective April 16; (6), (13), and (14) repealed, p. 1304, § 1, effective May 20; (9)(a), (9)(b), and (10) repealed, (10.1) R&RE, (11)(b)(I) and (12.2)(a) amended, and (12)(c) and (12.4) added, pp. 1388, 1386, 1385, §§ 6(1), 3, 1, 5, 2, effective June 20; (1) amended, p. 1383, § 1, effective July 10; (10.3) added, p. 1387, § 4, effective January 1, 1991; (9)(d) and (11)(c) added by revision, p. 1388, § 6(2). L. 88: (8) repealed, (9)(c), (9)(d), (10.1)(b), (10.3)(a), (11)(a), (11)(b)(I), (11)(c), and (12.3)(a) amended, (10.1)(d) R&RE, and (10.2) added, pp. 1275, 1269, 1273, 1270, §§ 14, 5, 6, 5, effective May 29; (1.5) R&RE, (16)(c) amended, and (16)(d) added, pp. 1279, 1282, §§ 2, 5, effective January 1, 1989; L. 89: (11)(b)(I) amended, p. 1450, § 2, effective June 7; (10.3)(c) amended, p. 1644, § 8, effective January 1, 1991. L. 90: (16)(d) repealed, p. 1840, § 19, effective May 31; (12)(c) repealed and (16)(a) and (16)(c) amended, pp. 1705, 1689, §§ 41, 4, effective June 9. L. 91: (10.2)(c), (10.3)(a), (11)(a)(I), (11)(b)(I), and (12.4) amended and (10.2)(e) and (11)(c) repealed, pp. 2003, 2005, §§ 1, 5, effective June 6. L. 92: (11)(b)(I) amended, p. 2212, § 10, effective June 3. L. 93: (7) repealed, p. 1689, § 8, effective June 6. L. 94: (11)(b)(I) amended, p. 309, § 1, effective March 22. L. 95: (10.2)(c) and (10.3) repealed, p. 7, § 1, effective March 9. L. 96: (11)(a)(I), IP(12.2)(a), (12.3)(a)(I), and (12.4) amended, pp. 1198, 1199, §§ 1, 2, effective June 1. L. 99: (10.2)(d) amended, p. 202, § 1, effective August 4. L. 2002: (16)(a) amended, p. 861, § 1, effective August 7. L. 2005: (IP)(12.2)(a) amended, p. 781, § 72, effective June 1. L. 2020: (1.5) repealed,(SB 20-223), ch. 291, p. 1436, § 2, effective January 1, 2021. L. 2021: (1) and (4) amended and (1.6) and (1.8) added,(SB 21-293), ch. 301, p. 1806, § 2, effective June 23; (12.3)(a)(I) amended,(HB 21-1312), ch. 299, p. 1792, § 5, effective July 1. History. Source: L. 64: R&RE, p. 676, § 1. C.R.S. 1963: § 137-1-4. L. 65: P. 1096, § 2. L. 67: P. 946, § 5. L. 70: Pp. 380, 388, §§ 10, 28. L. 73: P. 1430 § 1. L. 75: (5) and (6) added, pp. 863, 1474, §§ 2, 1, effective July 1; (7) added, p. 1454, § 1, effective July 30. L. 76: (9) added, p. 755, § 5, effective July 1; (8) added, p. 755, § 4, effective January 1, 1977. L. 77: (10) R&RE and (11) and (12) added, pp. 1731, 1732, §§ 4, 5, effective June 20. L. 79: (13) added, p. 1329, § 2, effective May 8; (6) R&RE and (14) added, pp. 1403, 1327, §§ 1, 4, effective July 1; (2) amended, p. 1402, § 1, effective January 1, 1980. L. 80: (10) amended, p. 714, § 1, effective February 29; (9) amended, p. 711, § 1, effective April 16. L. 81: (13)(b) amended, p. 1836, § 1, effective June 4; (9)(a), (10)(a), (10)(b), and IP(12) amended, p. 1830, § 2, effective June 12; (12)(c), (12)(d), (12)(g), and (12)(h) amended, pp. 1848, 1854, §§ 4, 2, effective January 1, 1982; (16) added, p. 1397, § 8, effective January 1, 1983. L. 82: (11)(b) amended, p. 553, § 1, effective May 3; (16) amended, p. 457, § 2, effective January 1, 1983. L. 83: (2), (7), and (12.3)(b) repealed and (12.3)(a)(I) and (16) amended, pp. 1485, 1482, §§ 11, 3, effective April 22; (10), (11)(a), (11)(b)(I), and (12)(h) amended and (10.1), (12.1), and (12.2) added, pp. 1494, 1495, §§ 1, 2, effective April 28; (5) repealed, p. 2081, § 1, effective January 1, 1984. L. 84: (15) repealed, p. 999, § 3, effective January 1; (10), (10.1)(a), (12)(h), (12.1), IP(12.2)(a), and (12.2)(b) amended, p. 988, § 1, effective February 23. L. 85: (4) amended, p. 1212, § 8, effective May 9. L. 86: (16)(a) amended, p. 1101, § 1, effective March 26. L. 87: (16)(c) added, p. 1417, § 1, effective March 13; (12)(a) RC&RE and (12.2)(a) amended, p. 1390, §§ 1, 2, effective April 1; (12)(b) RC&RE and (12.2)(a) amended, p. 1392, §§ 1, 2, effective April 1; (1.5) added, p. 1384, § 1, effective April 16; (6), (13), and (14) repealed, p. 1304, § 1, effective May 20; (9)(a), (9)(b), and (10) repealed, (10.1) R&RE, (11)(b)(I) and (12.2)(a) amended, and (12)(c) and (12.4) added, pp. 1388, 1386, 1385, §§ 6(1), 3, 1, 5, 2, effective June 20; (1) amended, p. 1383, § 1, effective July 10; (10.3) added, p. 1387, § 4, effective January 1, 1991; (9)(d) and (11)(c) added by revision, p. 1388, § 6(2). L. 88: (8) repealed, (9)(c), (9)(d), (10.1)(b), (10.3)(a), (11)(a), (11)(b)(I), (11)(c), and (12.3)(a) amended, (10.1)(d) R&RE, and (10.2) added, pp. 1275, 1269, 1273, 1270, §§ 14, 5, 6, 5, effective May 29; (1.5) R&RE, (16)(c) amended, and (16)(d) added, pp. 1279, 1282, §§ 2, 5, effective January 1, 1989; L. 89: (11)(b)(I) amended, p. 1450, § 2, effective June 7; (10.3)(c) amended, p. 1644, § 8, effective January 1, 1991. L. 90: (16)(d) repealed, p. 1840, § 19, effective May 31; (12)(c) repealed and (16)(a) and (16)(c) amended, pp. 1705, 1689, §§ 41, 4, effective June 9. L. 91: (10.2)(c), (10.3)(a), (11)(a)(I), (11)(b)(I), and (12.4) amended and (10.2)(e) and (11)(c) repealed, pp. 2003, 2005, §§ 1, 5, effective June 6. L. 92: (11)(b)(I) amended, p. 2212, § 10, effective June 3. L. 93: (7) repealed, p. 1689, § 8, effective June 6. L. 94: (11)(b)(I) amended, p. 309, § 1, effective March 22. L. 95: (10.2)(c) and (10.3) repealed, p. 7, § 1, effective March 9. L. 96: (11)(a)(I), IP(12.2)(a), (12.3)(a)(I), and (12.4) amended, pp. 1198, 1199, §§ 1, 2, effective June 1. L. 99: (10.2)(d) amended, p. 202, § 1, effective August 4. L. 2002: (16)(a) amended, p. 861, § 1, effective August 7. L. 2005: (IP)(12.2)(a) amended, p. 781, § 72, effective June 1. L. 2020: (1.5) repealed,(SB 20-223), ch. 291, p. 1436, § 2, effective January 1, 2021. L. 2021: (1) and (4) amended and (1.6) and (1.8) added,(SB 21-293), ch. 301, p. 1806, § 2, effective June 23; (12.3)(a)(I) amended,(HB 21-1312), ch. 299, p. 1792, § 5, effective July 1.    Editor's note:    Subsection (12.1) provided for the repeal of subsections (12) and (12.1), effective January 1, 1987. (SeeL. 84, p. 988.)    Subsection (9)(d) provided for the repeal of subsections (9)(c) and (9)(d), effective January 1, 1989. (SeeL. 88, p. 1269.)    Subsection (10.1)(d) provided for the repeal of subsection (10.1), effective January 1, 1991. (SeeL. 88, p. 1273.)    Section 5(2) of chapter 291 (SB 20-223), Session Laws of Colorado 2020, provides that changes to this section take effect on the date of the governor's proclamation or January 1, 2021, whichever is later, only if, at the November 2020 statewide election, a majority of voters approve the ballot issue referred in accordance with section 2 of Senate Concurrent Resolution 20-001. The ballot issue, referred to voters as amendment B, was approved on November 3, 2020, and was proclaimed by the Governor on December 31, 2020. The vote count for the measure was as follows:     FOR: :u720 1,740,395   AGAINST: :u720 1,285,136   Cross references:    For constitutional provisions concerning taxation, see article X of the state constitution; for the provision that sets the valuation for assessment of residential real property at 21%, see § 3 (1)(b) of article X of the state constitution.    For the legislative declaration in HB 21-1312, see section 1 of chapter 299, Session Laws of Colorado 2021.     ANNOTATION   Law reviews. For article, “Property Tax Assessments in Colorado”, see 12 Colo. Law. 563 (1983). For article, “Appealing Property Tax Assessments”, see 15 Colo. Law. 798 (1986). For article, “Delinquent Oil and Gas Ad Valorem Taxes: Protecting Property Interests”, see 16 Colo. Law. 798 (1987).   Annotator's note. The following annotations include cases decided under former provisions similar to this section.   General assembly may constitutionally classify movable structures differently than conventional residences for tax purposes. Am. Mobile Home Ass'n v. Dolan, 191 Colo. 433 , 553 P.2d 758 (1976).   When cyclical revaluation plan deemed unconstitutional. A cyclical revaluation plan is violative of constitutional equality and uniformity standards only where its implementation results in intentional discrimination, arbitrary action, constructive fraud, or grossly and relatively unfair assessments. Nuttall v. Leffingwell, 193 Colo. 137 , 563 P.2d 356 (1977).   This section does not constitute retrospective legislation in violation of constitution. A change in the method of valuation during the year for which the assessment was made does not constitute retrospective legislation. Martin v. Bd. of Assess. Appeals, 707 P.2d 348 (Colo. 1985) (decided under law in effect prior to 1983 amendment).   It is duty of tax assessor to tax uniformly. Citizens' Comm. for Fair Prop. Taxation v. Warner, 127 Colo. 121 , 254 P.2d 1005 (1953).   All taxable property need not be revalued before individual revaluations are entered on the tax rolls. Nuttall v. Leffingwell, 193 Colo. 137 , 563 P.2d 356 (1977).   Federal statute prohibiting discriminatory tax treatment of airline property under provisions of this section does not apply retroactively to property taxes assessed prior to effective date of federal statute. State Bd. of Equaliz. v. Am. Airlines, 773 P.2d 1033 (Colo. 1989), cert. denied, 493 U.S. 851, 110 S. Ct. 151, 105 L. Ed. 2d 109 (1989).   Depreciation required to be calculated annually from the base year to the date of assessment for valuing personal business property. BQP Industries v. State Bd. of Equaliz., 694 P.2d 337 (Colo. App. 1984).   Statute does not permit consideration of subsequent economic conditions in determining property's base year value. Carrera Place v. Bd. of Equaliz., 761 P.2d 197 (Colo. 1988) (decided under law in effect prior to 1987 amendments).   Thus, additional hotel rooms that had not yet been constructed during the base period could not be considered in calculating the occupancy rate used to determine the actual value of a hotel for purposes of property taxation. Padre Resort, Inc. v. Jefferson County Bd. of Equaliz., 30 P.3d 813 (Colo. App. 2001).   It is proper for the board to consider evidence of other sales of comparable property within the base period which were similarly subject to long-term leases. Bd. of Assess. Appeals v. City and County of Denver, 829 P.2d 1319 (Colo. App. 1991), aff'd, 848 P.2d 355 (Colo. 1993).   Evidence of property tax valuations of the property for prior tax years is relevant to valuation issues concerning the current tax year, especially when the prior tax year is in the same reassessment cycle and the valuation is determined using the same base period. Weingarten v. Bd. of Assess. Appeals, 876 P.2d 118 (Colo. App. 1994).   Comparative sales data must be adjusted for time. In case where property owner appealed county assessor's valuation of the property to the board of assessment appeals, the board erred in reaching an alternative valuation without applying a time adjustment to the comparable sales data on which it relied. Adjustment for time under subsections (10.2)(a) and (10.2)(d) is not discretionary, but mandatory. Kidder v. Chaffee County Bd., 312 P.3d 1181 (Colo. App. 2011).   Correction of incorrect value in intervening year required. When an assessor learns of an incorrect assessment, subsection (11)(b)(I) requires the assessor to correct the assessment in an intervening year in order to set the value at what it would have been set at in the assessment year if the mistake had not occurred. Further adjustments to the value, however, cannot be made in an intervening year absent proof of an unusual condition. Thibodeau v. Denver County Bd. Comm'rs, 2018 COA 124 , 428 P.3d 706.   Although an assessor is not prevented from taking into account any unusual conditions related to real property which would result in an increase or decrease in actual value and may revalue property for an intervening year to rectify an incorrect base value assessment, an assessor may not revalue a property in an intervening year that has been correctly assessed, except as necessary to reflect the increase or decrease in actual value attributable to an unusual condition. Leavell-Rio Grande v. Bd. of Assess. Appeals, 753 P.2d 797 (Colo. App. 1988).   Unusual conditions affecting actual value are factors for consideration by the assessor in assessing real property. Depreciation factors apply only to personal property. CF & I Steel Corp. v. Patton, 765 P.2d 586 (Colo. App. 1988), rev'd on other grounds, 785 P.2d 605 (Colo. 1990).   “Unusual conditions” are set forth in two distinct provisions, of which one is limited and exclusive and the other is broadly inclusive. Where a contract for purchase and sale of the subject property was entered into in an intervening year, resulting in a difference in valuation of more than ten percent when compared with the valuation in effect during the normally applicable base period, evidence of the sale price was relevant under this section and should have been considered. Roberts v. Bd. of Assess. Appeals, 883 P.2d 588 (Colo. App. 1994).   “Unusual conditions” provisions apply to individual properties, not only to all properties in an entire neighborhood of like properties. Roberts v. Bd. of Assess. Appeals, 883 P.2d 588 (Colo. App. 1994).   Evidence relating to the amount stipulated to in adjudicatory proceedings and not to the assessor's original base period valuation was irrelevant as a matter of law to the unusual condition exception. Lowe Denver Hotel Ass'n v. Arapahoe County Bd. of Equaliz., 890 P.2d 257 (Colo. App. 1995).   The cost to cure environmental contamination, when mandated by a governmental entity, should be deducted from the valuation of the property for ad valorem tax purposes. E.I. du Pont de Nemours & Co. v. Douglas County Bd. of Equaliz., 75 P.3d 1129 (Colo. App. 2003).   E.I. du Pont de Nemours & Co. cited above does not address the exact manner in which governmentally ordered remediation costs to cure environmental contamination are to be deducted under the income approach, nor does it mandate any specific methodology, or require the deduction of the entire cost of remediation. Here, methodology of estimating annual income, subtraction of an annual cost to cure, and application of a capitalization rate to arrive at a taxable value of property capable of generating income is in conformity with the direct capitalization method of the income approach and supported by competent evidence. Microsemi Corp. v. Broomfield County Bd. of Equaliz., 200 P.3d 1123 (Colo. App. 2008).   A shut down of a portion of a plant does not constitute a change in the use of the land. LaDuke v. CF & I Steel Corp., 785 P.2d 605 (Colo. 1990).   The general assembly intended to authorize assessors to make “corrective” intervening year revaluations only when the assessor's original base period valuation for the first year of the reassessment cycle is subsequently asserted to be incorrect and, therefore, in need of correction. Lowe Denver Hotel Ass'n v. Arapahoe County Bd. of Equaliz., 890 P.2d 257 (Colo. App. 1995).   Statute does not authorize assessors to make intervening revaluations when the valuation for the first year of the cycle has been determined in adjudicatory proceedings resulting from taxpayer protests or appeals. Lowe Denver Hotel Ass'n v. Arapahoe County Bd. of Equaliz., 890 P.2d 257 (Colo. App. 1995).   Section 39-1-103 (8)(a)(I) , not subsection (12.3) of this section, applies to the valuation of real property. Since the 18-month time limitation for information used in property valuation applies exclusively to real property, the computer pricing guides used by the taxpayer need not conform to those time limitations. Bd. of County Comm'rs v. IBM Credit Corp., 888 P.2d 250 (Colo. 1995).   Obsolescence may be a relevant factor in determining the actual value of personal property. IBM Credit Corp. v. Bd. of County Comm'rs, 870 P.2d 535 (Colo. App. 1993).   Under subsection (12.3), if an approach to value is applicable, it must be given appropriate consideration by the assessor, as well as by the board of assessment appeals, as the trier of fact. Home Depot USA, Inc. v. Pueblo County Bd. of Comm'rs, 50 P.3d 916 (Colo. App. 2002).   Applied in First Nat'l Bank v. Bd. of Comm'rs, 36 Colo. 265 , 84 P. 1111 (1906); Bd. of County Comm'rs v. Bd. of Assess. Appeals, 628 P.2d 156 (Colo. App. 1981).