Types of Bill of Materials: EBOM, MBOM, SBOM and the Rest, Explained

Engineering BOM (EBOM): the product as designed

The engineering BOM is the design view. It comes out of CAD or out of the engineer’s head, and it is organised the way the product is conceived — functional groupings, design assemblies, part numbers as drawn. It answers “what is this thing made of, in principle?”

Who owns it: design or engineering. In a ten-person fabricator, that is usually one person and a folder of drawings.

What it contains: designed parts, quantities, part numbers, revision level, drawing links. What it omits: fasteners bought by the kilo, adhesives, packaging, paint, the jig you need, the offcut you always scrap, and the order in which anything is done.

Oracle’s Bills of Material documentation treats engineering bills as alternates to manufacturing bills, typically used to prototype variations that produce the same assembly — which is a fair description of how the EBOM behaves in practice. It is the version that changes fastest and matters least to the shop floor until it is released.

Manufacturing BOM (MBOM): the product as built

The manufacturing BOM is the production view. It restructures the EBOM around how the thing is physically made: build stages, sub-assemblies that exist because of the process rather than the design, and every consumable that gets used up on the way.

Who owns it: production or operations. It is the BOM that drives purchasing, works orders, material issues and job costing.

The MBOM is nearly always the longer list, because it carries everything the drawing never had to mention. That length is the point: it is the version purchasing and job costing both read from.

On the pair itself, two sentences and no more, because the comparison has its own page: the EBOM is design intent and the MBOM is build reality, and the handover between them — release, restructure, add process material — is the single most common place BOM data goes wrong. If that transition is your actual problem, read engineering vs manufacturing BOM rather than this list.

Sales BOM and configurable BOMs: the product as sold

A sales BOM describes what the customer buys, which is not always what the factory builds. Two common shapes:

• Kit or sales-kit BOM. The customer orders one line; the system ships several. A bundle, a starter pack, a machine plus its install kit. Stock moves at component level, the order shows one item.
• Configurable or model BOM. The customer picks options and the buildable product is assembled from those choices. Oracle describes a model bill as one that defines the options and option classes available for ordering, where the model itself is never ordered or built — only its configurations are, with an “option class” grouping the choices at one level (monitor as a class, specific monitors as options).

Who owns it: sales, with engineering signing off on which combinations are actually valid. That sign-off is the part that matters. A configurable BOM without validity rules is a machine for selling things you cannot build.

Signal you need one: quotes are assembled by copying last month’s quote and editing it, and too many come back from production with “we can’t do that with that motor”.

Service and spare-parts BOMs: the product as maintained

The service BOM lists what a field engineer or a customer needs to keep the product running: replaceable parts, wear items, seals, filters, consumables, and often the tools and instructions that go with them. A spare-parts BOM is the narrower version — just the items you sell as spares.

Who owns it: aftersales or service. In smaller firms, whoever answers the phone when a customer says the door won’t close.

This is the most under-built BOM type in small manufacturing and often the most profitable. Spares carry better margin than the original unit, and demand is predictable once you know which three parts fail. Without a service BOM that knowledge lives in one engineer’s memory and walks out with them.

Template, assembly, phantom and planning BOMs: the structural set

The remaining types are not about audience at all. They exist to make reuse, structure and forecasting work, and they are the ones that appear in ERP documentation and confuse people looking for a straight answer.

• Template BOM. A skeleton for a family of products, copied and adjusted per job. Common in made-to-order fabrication and joinery, where every unit differs but most of the list repeats. It kills the “start from a blank spreadsheet” habit that produces omissions.
• Assembly or sub-assembly BOM. A BOM for a component that is itself built, then consumed by a parent. This is what turns a flat list into a structure, and it is the mechanism behind multi-level BOMs. The test: do you ever hold it in stock, sell it, or build it ahead of the parent? If yes, give it a BOM. If it only exists mid-shift on a bench, use a phantom.
• Phantom BOM. Oracle defines a phantom assembly as a nonstocked assembly that lets you group materials required to produce a subassembly. Planning “blows through” it to the components, so the phantom’s parts appear on the job while the phantom itself never does. Use it for a grouping that is real on the bench but never in the stockroom.
• Planning BOM. An artificial parent used for forecasting rather than building. Oracle’s planning bill carries a percentage distribution across components, and notably the percentages need not add up to 100%. You forecast “500 units of the task-chair family” and the planning BOM splits that across variants.
• Modular BOM. The family broken into interchangeable modules so you plan and stock modules rather than every finished permutation. The natural partner to a configurable sales BOM.
• Batch and percent BOMs. Process-industry structures. A batch BOM is stated per production batch rather than per unit; a percent BOM states components as proportions of the batch. Oracle’s JD Edwards documentation lists planning, batch, percent and manufacturing bills as distinct types for exactly this reason. If you make paint, food, cosmetics or chemicals, these are not exotic — they are your normal.

Ownership is production engineering for the reuse types and planning for the rest — or nobody, which is usually why they are wrong.

“SBOM” means three different things — get the acronym straight

This trips people up constantly, and the search results rarely separate them.

1. Sales BOM. The kit or configurable list described above. Most common meaning inside a manufacturing ERP.
2. Service BOM. The spares and maintenance list. Equally common, and the reason “SBOM” is genuinely ambiguous in a manufacturing conversation.
3. Software Bill of Materials. A completely different discipline. NIST, summarising Executive Order 14028, defines it as a formal record containing the details and supply chain relationships of various components used in building software — an ingredients label for code, used to trace vulnerabilities.

If your product contains firmware and you sell into regulated or public-sector buyers, you may end up needing both a service BOM and a software SBOM, and they have nothing in common except the acronym. When someone in a meeting says “SBOM”, ask which one before agreeing to produce it.

Types of bill of materials compared: purpose, owner, what breaks

A worked example: one office chair, four BOMs

A UK furniture manufacturer builds a task chair to order. One product, four legitimate lists.

EBOM (from the drawing): seat pan, backrest frame, mesh panel, gas lift cylinder, five-star base, castor set, armrest pair, tilt mechanism. Eight lines, structured the way the product was designed.

MBOM (from the shop floor): those eight restructured into three build stages — sub-assemble the seat, sub-assemble the base, final assembly — plus the foam adhesive, the staples, the thread-lock, the fitting bag, the assembly instructions, the polybag and the double-wall carton. Around eighteen lines. The extra ten are the ones nobody costs, and together they are the difference between the job making money and looking like it did.

Sales BOM (from the quote): base chair as one orderable line, with an option class for mesh colour (six options), one for armrests (fixed, adjustable or none) and an optional headrest that ships as a kit BOM. The customer sees three choices; the factory sees a validated configuration.

Service BOM (from the field): gas lift cylinder, castor set, armrest pad, tilt-tension knob. Four lines. These are the only parts anyone has ever phoned about, and they are sold at spares margin.

Same chair. Four lists, four owners, four jobs. Run all four from one spreadsheet tab and you get a list that is too long for the salesperson, too short for the buyer and out of date for the engineer.

Which types of bill of materials a growing UK manufacturer actually needs

Be honest about the stage you are at. The realistic sequence:

Stage one — you need one BOM, done properly. A single accurate list per product, with revisions, that production and purchasing both work from. Most firms calling their list an “EBOM” have not yet got this. Fix accuracy before you multiply views.

Stage two — split EBOM and MBOM. The trigger is repeated cost surprises on jobs, or engineering changes reaching the floor late. This is the highest-value split for a fabricator, machine builder or assembler, and it is where BOM software starts to pay for itself.

Stage three — add whichever of sales or service applies. Configure-to-order businesses need the sales BOM. Installed-base businesses with machines in the field need the service BOM. Most firms do not need both at once; pick the one attached to the revenue you are actually losing.

Stage four — templates and assembly BOMs. Once you have families rather than one-offs, the reuse layer stops rework. Cheap to add if the underlying data is clean.

Stage five — planning, modular, phantom, batch/percent. Add them when volume and variant count make forecasting a real activity rather than a guess — or immediately, if you are a process manufacturer, where batch and percent BOMs are stage one.

The common failure is jumping to stage five vocabulary while stuck at stage one accuracy. A phantom BOM on top of a wrong parts list is just a faster way to be wrong.

Where multiple BOM types fall apart in spreadsheets

A spreadsheet can hold one BOM well. It handles several views of the same product badly, for structural reasons rather than snobbery.

• No single source. Four tabs means four truths. Change the hinge supplier and you update one of them.
• No revision control. “Chair BOM v4 FINAL (Dave’s copy)” is not a revision. When the floor builds from the wrong file, the scrap is real.
• No link between views. A change to the EBOM ought to raise a question against the MBOM. In a spreadsheet it raises nothing.
• No validation on configurations. Nothing stops a quote combining a lock type with a door that cannot take it.
• No consumption. The BOM does not reduce stock when a job is issued, so the figure drifts until the next count.

The fix is not necessarily a full ERP. For a business too messy for spreadsheets but not ready for one, a right-sized operations system holds a single product record with several BOM views hanging off it — designed, built, sold, serviced — where a change in one raises a flag against the others, issuing a works order actually moves stock, and the whole thing is built around how you make things rather than a platform you reshape yourself around.

FAQ

How many types of bill of materials are there?

There is no fixed number, because BOM types are defined by purpose rather than by a standard. The widely used set is engineering, manufacturing, sales/configurable, service/spare-parts, template, assembly, phantom, planning, modular, batch and percent. ERP vendors add their own — Oracle documents standard, model, option class, planning and engineering bills, while its JD Edwards line lists planning, batch, percent and manufacturing bills. Treat the list as a menu, not a checklist.

What is the difference between a sales BOM and a kit BOM?

A kit BOM is the simpler case: the customer orders one line, the system ships several components, and there is nothing to choose. A sales BOM in the fuller sense is configurable — the customer picks from option classes and the buildable product is assembled from those choices, which is what Oracle calls a model bill. Every kit is a sales BOM; not every sales BOM is a kit.

Does SBOM mean sales BOM or software bill of materials?

Both, plus service BOM — the acronym is genuinely overloaded. In a manufacturing ERP conversation it usually means a sales BOM or a service BOM. In a cybersecurity or procurement conversation it means a Software Bill of Materials, defined by NIST as a formal record of the components and supply chain relationships used in building software. Ask which one is meant before committing to produce it.

Which BOM type should a small manufacturer start with?

One accurate manufacturing BOM per product, including consumables and packaging. It is the version that drives purchasing, works orders and job costing, so it is the one whose inaccuracy costs money immediately. Add an engineering view once design changes start reaching the floor late, and a sales or service BOM once quoting or spares becomes a repeatable revenue stream.

Sources

• Oracle Bills of Material — Overview of Bills of Material — definitions of standard, model, option class, planning and engineering bills.
• Oracle SCM Cloud — How Phantom Assemblies Are Used in Supply Chain Planning — phantom definition and planning behaviour.
• Oracle JD Edwards EnterpriseOne — Understanding Types of Bills of Material — planning, batch, percent and manufacturing bills.
• NIST — Software Security in Supply Chains: Software Bill of Materials (SBOM) — the Executive Order 14028 SBOM definition.