ADS is Alternative Depreciation System.  "Straight-Line" uses the General Depreciation System

Although ADS uses Straight Line, many types of assets are have a larger Recovery Period (number of years it is depreciated over).  But in some cases, it is the same.

Here is some more information about the straight line method:

Straight Line Method

This method lets you deduct the same amount of depreciation each year over the useful life of the property. To figure your deduction, first determine the adjusted basis, salvage value, and estimated useful life of your property. Subtract the salvage value, if any, from the adjusted basis. The balance is the total depreciation you can take over the useful life of the property.

Learn more from the IRS here.

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