Absorption (Total) costing is a method of costing where all overheads must be allocated to products. It calculates the full production cost per unit by including both direct and indirect costs. Overheads are apportioned to cost centers and production departments based on factors like floor area, assets, orders, or personnel. Overhead absorption rates are set based on planned production volumes and budgets to determine the overhead amount recovered from each unit. Differences between actual and planned overhead expenditures and production volumes can lead to over-absorption or under-absorption of overheads.