Which of the following would affect the taxpayer who owns commercial property but not one owning residential property when computing federal income taxes?

Depreciation is the correct answer because it is a tax benefit that specifically applies to commercial property owners when calculating federal income taxes. Depreciation allows property owners to deduct the wear and tear on their properties over time, which can significantly reduce their taxable income. Commercial properties are often subject to this deduction, providing the owner a means to lower their tax liability on earnings generated by the property.

In contrast, while depreciation can be applied to residential rental properties as well, the question specifies an effect that distinctly impacts commercial property owners. The nuances related to how and when commercial versus residential depreciation can be claimed, including potential differences in recovery periods and methods, can vary greatly and have a more pronounced impact on commercial property owners, especially when factoring in aspects like business expenses or operational costs. Additionally, commercial properties often face different tax implications and regulations than residential properties, further emphasizing the significance of depreciation in this context.

Property taxes, interest, and gains on sales apply to both commercial and residential properties and would not provide a distinction in tax calculations based solely on property type. Therefore, depreciation stands out as the aspect that uniquely affects the commercial property taxpayer.