✦ Sector
Inventory management for manufacturers: raw materials to finished goods
Inventory management for manufacturing isn't one stock figure - it's raw materials, work in progress and finished goods, each behaving differently, all linked by a bill of materials that determines what a finished item actually consumed to get made.
Haystak · 12 August 2026 · Updated 12 August 2026 · 8 min read
Inventory management for manufacturing tracks stock through three distinct states - raw materials waiting to be used, work in progress partway through a build, and finished goods ready to ship - and the movement between those states is governed by a bill of materials that says exactly what quantity of each material a finished unit consumes. That's fundamentally different from retail or distribution stock, where an item simply exists or doesn't.
Most of the inventory problems we see in manufacturing businesses come down to one of two things: the bill of materials not being kept accurate as products change, or work in progress being effectively invisible because nobody's tracking partially-built stock as a distinct thing worth counting.
Three kinds of stock, not one
A manufacturer's stock file needs to represent raw materials and components bought in, work in progress sitting on the shop floor mid-build, and finished goods ready for despatch, and it needs to move value and quantity between those three states as production actually happens, not just when someone remembers to update a spreadsheet.
| Stock state | What it represents | What tracking it badly costs you |
|---|---|---|
| Raw materials | Bought-in components and materials not yet consumed | Reordering too early or too late, and no visibility of what a job actually needs before it starts |
| Work in progress | Materials consumed but not yet a finished, sellable unit | No idea how much value is tied up on the shop floor, or how close a job actually is to completion |
| Finished goods | Completed units ready to sell or ship | Overselling capacity you don't actually have, or holding finished stock nobody can see |
The bill of materials is the link that has to stay accurate
A bill of materials (BOM) defines what quantity of each raw material or sub-assembly one unit of a finished product consumes. When a job is completed, the system should automatically reduce raw material stock by the BOM quantities and increase finished goods stock - and if the BOM is out of date because a product changed but nobody updated the record, every stock movement calculated from it will be wrong too.
This is one of the areas where types of manufacturing software genuinely diverge from general stock or ERP products - a system with a weak or bolted-on BOM model will always struggle to keep manufacturing inventory accurate, however good its general stock features are.
Work in progress is where visibility usually disappears
Raw materials get counted because they sit in a store with a clear location. Finished goods get counted because they're ready to ship. Work in progress - partially built units on the shop floor - is much easier to lose track of, because it doesn't sit neatly in one place and its value changes as more labour and material go into it.
- Record materials as issued to a job the moment they leave the store, not when the job finishes.
- Track job stage against a defined production process, tied to production scheduling rather than a separate tracker.
- Value work in progress at each stage so the business has a real figure for stock tied up mid-build, not just raw and finished stock.
- Reconcile scrap and rework against the job it came from, not as a general write-off.
Reordering raw materials against real demand
Reordering purely on a minimum stock level, without reference to confirmed orders and planned production, tends to either tie up cash in materials you don't need yet or leave you short when a job is scheduled. Material requirements planning - working back from a production schedule to what needs to be bought and by when - is the more reliable approach once you're running more than a handful of jobs at once, and it's covered in more depth in our guide to MRP vs ERP.
Traceability and lot tracking
Where materials need to be traced - food, pharmaceuticals, regulated components, or simply a warranty claim that needs to identify which batch a part came from - stock records need to carry lot or batch numbers through from goods-in to finished product, not just a total quantity. This overlaps closely with food traceability software for food manufacturers specifically, but the same principle applies to any regulated or safety-critical component.
Off-the-shelf vs bespoke for manufacturing inventory
Established manufacturing ERP and MRP products handle standard BOM-driven stock movement, work in progress tracking and material requirements planning well, and are a sensible starting point rather than building from scratch. Where they struggle is unusual production processes - configurable products with variable BOMs, byproducts and co-products, or a scheduling constraint tied to specific machinery that a standard product doesn't model.
That's where our manufacturing software work tends to focus - either a bespoke system built around the actual production process, or a bespoke module bolted onto a standard ERP core to handle the part that doesn't fit. Get in touch and describe your production process, and we'll give you a straight view on whether a standard product covers it.
✦ Where this fits
More on this from us: our manufacturing software work.