Which of the following is NOT a method of depreciation?

The cash basis method is not a method of depreciation. It refers to an accounting technique where revenue and expenses are recorded when cash is actually received or paid, rather than when they are incurred. In contrast, depreciation methods such as the straight-line method, declining balance method, and units of production method are specific techniques used to allocate the cost of tangible assets over their useful lives.

The straight-line method spreads the cost of an asset evenly over its expected life, making it straightforward and commonly used. The declining balance method accelerates the depreciation expense in the earlier years of an asset's life, reflecting the higher utility and decreased value over time. Lastly, the units of production method ties depreciation directly to the actual usage of the asset, making it suitable for assets whose wear and tear is more closely related to their operational output rather than the passage of time. Each of these methods serves to allocate the purchase cost of an asset systematically, which is distinct from the cash basis accounting method.