EME 460
Geo-Resources Evaluation and Investment Analysis

Depletion and Amortization



The owner of an economic interest in mineral deposits, oil and gas wells, or standing timber may recover his or her cost through federal tax deductions for depletion over the economic life of the property. Oil, gas, and mineral depletion is computed by two methods: 1) cost depletion and 2) percentage depletion. Only cost depletion applies to timber. For petroleum and mining, both cost and percentage depletion must be computed each year. The result that gives the largest allowable tax deduction, accounting for the 50% or 100% percentage depletion limits applicable to mining and petroleum producers, is used later as described. One can switch methods from year to year with the exception that integrated oil and gas producers may only take cost depletion on oil and gas properties. More information about depletion can be found at IRS website.


It is permissible for a business to deduct each year as amortization a proportionate part of certain capital expenditures. Amortization permits the recovery of these expenditures in a manner similar to straight line depreciation over five years, or a different specified life. As a general rule, amortization relates to intangible asset costs while depreciation relates to tangible asset costs. However, only certain specified expenditures may be amortized for federal income tax purposes. You can find more detailed information about amortization at IRS website.

Italicized sections are from Stermole, F.J., Stermole, J.M. (2014) Economic Evaluation and Investment Decision Methods, 14 edition. Lakewood, Colorado: Investment Evaluations Co.