work-in-process

Operational meaning

Work-in-process (WIP) commonly refers to all partially completed units, assemblies, or lots that are somewhere between the release of raw materials and the completion of finished goods. It includes any product that has entered a production process but has not yet passed all required operations, tests, and verifications.

In accounting and inventory terms, WIP is usually tracked as a distinct category from raw materials and finished goods. It may carry both material and applied labor/overhead value, depending on the costing method used.

Use in manufacturing and regulated environments

In industrial and regulated manufacturing environments, work-in-process typically includes:

– Components and assemblies in fabrication, machining, or subassembly operations
– Units in queue at work centers, test stations, or inspection points
– Kits that have been issued from stock and are being assembled
– Items that have been built but are waiting for required inspections, documentation, or release

WIP is often managed and tracked in MES and ERP systems using work orders, operations, routing steps, or production orders. Traceability requirements (for example in aerospace, pharma, or medical devices) mean WIP must usually be linked to:

– Specific orders, configurations, or serial numbers
– Material lots, batches, or heat numbers
– Process parameters, test results, and quality records

Boundaries and exclusions

Work-in-process generally includes:

– Any item that has been formally released to production and has at least one operation started
– Rework units that are back in process under controlled documentation

It generally excludes:

– Raw materials or components that have not yet been issued to a production order
– Finished goods that have completed all required operations, tests, and documentation and are ready for shipment or stocking as sellable inventory
– Spare parts or service parts held outside of active production

Relation to systems and inventory control

In integrated ERP–MES–shop floor environments, WIP is usually represented by:

– Open production orders and their current operation/step
– Quantities at each work center or buffer location
– Status codes (for example, in-process, on hold, under inspection, in rework)

Accurate WIP tracking is important for:

– Inventory accuracy and financial valuation
– Schedule visibility and capacity planning
– Traceability and compliance in regulated industries

Physical WIP (what is actually on the floor) can diverge from system WIP (what ERP/MES shows) when transactions are delayed, workarounds are used, or routing and documentation do not match real practices.

Common confusion and alternate usage

Two near-synonymous terms are widely used:

– **Work-in-process (WIP)** – more common in manufacturing of discrete items and regulated production contexts
– **Work-in-progress (WIP)** – often used interchangeably, especially in construction or project environments

On this site, both usually refer to physical or digital product units in an intermediate, unfinished production state. This should not be confused with:

– **Workload** or task queues for people or departments
– **Projects-in-progress** in engineering or IT, which may be tracked as WIP in project management but are not inventory

Site context: inventory inaccuracies and aerospace manufacturing

In aerospace and other highly regulated manufacturing, work-in-process is a frequent source of inventory discrepancies. Typical contributors include:

– Kits issued from ERP that are partially consumed or substituted on the floor without timely transactions
– Assemblies moving between operations or cells without proper WIP movement or booking
– Engineering changes that alter bills of material or routings while units are mid-process
– Rework performed under deviation or concession that is not reflected in system WIP quantities and locations

In this context, careful alignment between ERP, MES, and shop-floor practices is needed so that system records of WIP quantities, locations, and statuses match the actual physical items in process.