For any manufacturer running NetSuite, production runs through a chain of connected concepts: the Bill of Materials (BOM), the Assembly Item, the Work Order, Work-in-Process (WIP), and Routings — with Advanced Manufacturing available for businesses that need to go further still. Get these set up well, and inventory, costing, and scheduling all flow cleanly. Get them wrong, and you’ll spend a lot of time reconciling numbers that don’t add up. This guide walks through how each piece fits together, including a worked example using yield and formula-based manufacturing — an area that trips up a lot of NetSuite implementations.
The three building blocks
Bill of Materials (BOM): the recipe. It lists every component, sub-assembly, and quantity needed to build one unit of a finished item. In NetSuite this is captured on the Assembly Item record itself, or via the Manufacturing module if you’re using multi-level or revision-controlled BOMs.
Assembly Item: the finished (or semi-finished) product that the BOM produces. It behaves like an inventory item, but it also carries the component list and the build logic behind it.
Work Order: the instruction to actually build something. It pulls the BOM, reserves or consumes the component inventory, and — once completed — receives the finished assembly into stock at a calculated cost.
Together, these three answer three separate questions: what goes into this product (BOM), what are we building (Assembly Item), and are we building it right now (Work Order).
A straightforward example
Say you build a metal bracket assembly from a base plate, two brackets, and a set of fasteners. The BOM specifies the quantities, the Assembly Item defines the finished bracket assembly, and a Work Order for 100 units consumes 100 base plates, 200 brackets, and 100 fastener sets, then receives 100 finished assemblies into inventory at standard or actual cost.
That’s the easy case: one unit of output per one unit of “recipe.” Fixed ratios in, fixed output out.
Where it gets interesting: formula and yield-based manufacturing
Fixed-ratio BOMs work well for discrete manufacturing — brackets, machined parts, sub-assemblies. They work far less well for process or formula manufacturing, which is common across chemicals, plastics, food & beverage, and other blended or reactive processes. Here, the output isn’t a fixed multiple of the inputs. Batches vary, moisture evaporates, reactions aren’t 100% efficient, and scrap happens.
This is where yield management comes in, and it’s one of the more overlooked configuration points in NetSuite manufacturing setups.
Worked example: a liquid coating formula
Imagine a coatings manufacturer producing a 1,000-litre batch of a specialty finish from a formula of resin, solvent, and additive:
| Component | Formula Quantity |
| Resin | 600 L |
| Solvent | 350 L |
| Additive | 60 L |
| Total input | 1,010 L |
On paper the formula totals 1,010 litres. But solvent flash-off during mixing and a small amount of transfer loss mean the actual usable output is closer to 970 litres — a yield of roughly 96%.
If the BOM is set up as a simple fixed-ratio recipe, NetSuite will assume 1,010 litres in produces 1,010 litres out. Every batch will then show a “phantom” gain or loss against standard cost, and inventory valuation will drift further from reality with every run. Multiply that across dozens of batches a month and the variance becomes a real reporting headache — and a hard one to explain at month-end.
Handled properly, the formula is built with an expected yield percentage applied against the BOM, so NetSuite’s projected output for a 1,010 L input batch is set at the realistic ~970 L, not the theoretical 1,010 L. The Work Order can then be closed against actual output quantity, with any variance between expected and actual yield flowing cleanly into a variance account rather than distorting the standard cost of the finished item.
The practical benefits of setting this up correctly:
- Costing stays accurate. The cost of the 60 litres “lost” to processing is absorbed correctly into the batch, rather than silently inflating the unit cost of everything downstream.
- Planning improves. MRP and demand planning can work off realistic yield expectations instead of theoretical ones, so you don’t chronically under- or over-produce against sales orders.
- Variance reporting becomes useful. Instead of vague “why doesn’t inventory match the GL” conversations, you get a clean yield variance report that shows exactly which batches ran hot, cold, or on-target.
- Scaling is safer. Formulas can be scaled up or down (a 1,000 L batch to a 5,000 L batch, for example) while the yield percentage — not just the raw quantities — scales with it.
WIP and Routings: two different things people often conflate
Once a Work Order is released, two more concepts come into play — Work-in-Process (WIP) and Routings — and it’s worth being clear on the difference, because they answer different questions.
Work-in-Process (WIP) is a financial and inventory state. From the moment a Work Order is released and components are issued, the value of those components moves out of raw materials and sits in a WIP account until the build is completed and the finished assembly is received into stock. WIP tells you: how much value is currently tied up in things that are partway through being built, right now. It’s a snapshot of cost, not of process.
Routings describe the sequence of operations a Work Order moves through to get built — for example, cutting, then welding, then painting, then inspection — each with its own work center, run time, and setup time. Routings tell you: what steps does this build go through, in what order, and how long should each one take. It’s a map of process, not of cost.
Put simply: WIP is about where the money sits mid-build; Routings are about where the job sits mid-build. A Work Order without routings still generates WIP the moment components are issued — it just won’t give you visibility into which operation the job is currently sitting at, or where a bottleneck is forming. Add routings, and WIP reporting becomes far more useful, because you can see cost accumulating operation-by-operation rather than as one lump sum released at the end.
For simple assemblies, basic WIP tracking is often enough. For multi-step production — machining, fabrication, multi-stage chemical processing — routings turn WIP from “a number” into a genuinely useful shop-floor and costing tool.
A note on Advanced Manufacturing
Everything above is achievable with NetSuite’s standard Manufacturing module, but for more complex operations, NetSuite’s Advanced Manufacturing functionality extends it further — things like multi-level routings across work centers, more granular operation-level costing, backflush consumption at specific routing steps, and tighter integration between planning (MRP) and the shop floor. It’s aimed at manufacturers who’ve outgrown basic BOM-and-Work-Order tracking and need real operation-by-operation visibility — particularly useful for engineer-to-order, multi-stage process manufacturing, or businesses running high volumes across several work centers at once. It’s not a fit for every manufacturer, but for the right operation it closes a lot of the gap between what NetSuite shows on paper and what’s actually happening on the shop floor.
A few practical setup notes
- Decide early whether you need simple Assembly BOMs or the full Manufacturing module (routings, operations, work centers) — yield management and multi-level formula manufacturing usually push you toward the latter.
- Build yield assumptions from real production data, not theoretical formula totals. A yield percentage that’s “close enough” on paper but wrong in practice defeats the purpose.
- Review yield variance regularly. Ingredient batches, equipment, and operators all drift over time, and a yield percentage set up two years ago may no longer reflect the shop floor.
- Keep BOM revisions controlled. When a formula changes — even slightly — the yield assumption often needs to change with it.
The bigger picture
Work Orders, BOMs, and Assembly Items are simple in concept but easy to under-configure, particularly for businesses moving from discrete to process manufacturing, or handling both side by side. Getting yield and formula management right isn’t just a system configuration detail — it directly affects costing accuracy, planning reliability, and how much you trust the numbers coming out of NetSuite.
If you’re evaluating your current setup, or bringing in specialist NetSuite talent to get this right, it’s worth having the conversation early rather than after a few quarters of unexplained variance.
