Backflush accounting is a certain type of "postproduction issuing", it is a product costing approach, used in a Just-In-Time (JIT) operating environment, in which costing is delayed until goods are finished. Standard costs are then flushed backwards through the system to assign costs to products. The result is that detailed tracking of costs is eliminated. Journal entries to inventory accounts may be delayed until the time of product completion or even the time of sale, and standard costs are used to assign costs to units when journal entries are made. Backflushing transaction has two steps: one step of the transaction reports the produced part which serves to increase the quantity on-hand of the produced part and a second step which relieves the inventory of all the component parts. Component part numbers and quantities-per are taken from the standard bill of material (BOM). This represents a huge saving over the traditional method of a) issuing component parts one at a time, usually to a discrete work order, b) receiving the finished parts into inventory, and c) returning any unused components, one at a time, back into inventory.
It can be argued that backflush accounting simplifies costing since it ignores both labour variances and work-in-process. Backflush accounting is employed where the overall business cycle time is relatively short and inventory levels are low.
Backflush accounting is inappropriate when production process is long and this has been attributed as a major flaw in the design of the concept. It may be also be inappropriate if the bill of materials contains not only piece goods but also many parts with more or less variable consumption. If the parts with variable consumption are just a few, like grease or the ink used to print product-labels, the consumed quantities can be assigned to product-independent cost centers at the withdrawal from stores (preproduction issuing) and can eventually be broken down afterwards to specific products or product groups, just like any other indirect or overhead expense. Difficulties maintaining correct inventories on shop floor may also appear if it is usual practice to use alternative materials and/or quantities without needing derogation. Therefore, in case of a more complex production system, it is a better approach to use a Manufacturing Execution System (MES) which gathers real production data and is able to deliver exact data to the accounting software or Enterprise resource planning-system where the goods issue is recorded. Thus, variances in consumption, in comparison to the standard bill of materials, are taken into account and assigned to the correct product, production order and workplace. Another advantage of using a MES is that it implements also the Production Track & Trace and the status of work in progress is also known in real time. A disadvantage of MES is that it is not suitable for small series or prototype production. Such type of production should be segregated from the series production and mass production.