In which timeframe are all expenses categorized as either variable or avoidable fixed costs?

The categorization of all expenses as either variable or avoidable fixed costs primarily occurs in the long run. In this context, the long run refers to a period sufficient enough for a business to adjust all inputs and costs, allowing for comprehensive decision-making regarding expenses. During this timeframe, firms can change their production processes, enter or exit markets, and make adjustments to avoidable fixed costs, which are costs that can be eliminated if a business decides to cease certain operations.

In contrast, in the short run, some costs are considered fixed and are not easily altered, regardless of the level of production. As such, certain fixed costs cannot be categorized purely as avoidable at this stage, as they may still be incurred even if production is momentarily scaled down. The other options, like immediate run and static run, are not commonly recognized terms in cost theory, making them less applicable in this context of expense categorization. Thus, the long run is the appropriate timeframe for classifying all expenses into the relevant categories effectively.