What Is Multi-Level BOM?
Also known as: indented BOM, multilevel bill of materials, BOM levels
Definition
A multi-level BOM lists a finished product and each of its sub-assemblies and components in nested levels, so you can see the full structure from the end item down to raw material, rather than only the immediate children.
Multi-Level BOM Explained
A single-level BOM shows only direct components. A multi-level BOM, often displayed as an indented BOM, expands each sub-assembly beneath its parent to the lowest purchased part. Level 0 is the finished good, level 1 its direct components, and so on.
Depth affects planning. MRP processes items by low-level code, the lowest level at which an item appears anywhere in any BOM, so that gross requirements for a shared part are totaled before it is planned. A bolt used at level 1 on one product and level 4 on another gets a low-level code of 4.
Depth also affects lead time and cost. Total lead time is the longest path of cumulative lead times down the structure, and rolled-up cost sums each level. Deep structures with unnecessary levels add transaction overhead, because each stocked sub-assembly needs its own work order, receipt and count. Phantom assemblies remove that overhead where the sub-assembly is never stocked.
In Infor LN, the multi-level view is available in the BOM and Item Production data screens, SyteLine offers a multi-level BOM inquiry through job-order and item screens, and NetSuite shows assembly components with an indented report. Names and layout vary.
Why It Matters
- Planning, costing and capable-to-promise all depend on the structure being complete and correctly leveled.
- Unneeded levels create work orders and transactions that add no value.
- Missing levels hide shortages until the final assembly is already late.
- Impact analysis for a part change requires walking the structure both up and down.
In Practice
A drive unit has 5 sub-assemblies, 2 of them containing their own sub-assemblies, for 4 levels and 60 unique parts. If the lowest sub-assemblies have 3-day lead time each, the minimum cumulative lead time is about 12 days before final assembly time is added, even if every purchased part is in stock.
Frequently Asked Questions
What is the difference between a single-level and multi-level BOM?
Single-level shows only direct children of one parent. Multi-level expands every sub-assembly down to purchased parts.
What is a low-level code?
It is the deepest level at which an item appears in any BOM. MRP uses it to net each part only after all parents have been planned.
How many BOM levels is too many?
There is no fixed number. If a level is never stocked, built separately or costed, convert it to a phantom and flatten the transaction flow.
Related Terms
BOM (Bill of Materials)
A BOM (bill of materials) is the structured, hierarchical list of components, sub-assemblies, and quantities required to produce one unit of a parent item, and it is the primary input MRP explodes to calculate material requirements.
MRP (Material Requirements Planning)
MRP (Material Requirements Planning) is the ERP calculation that explodes demand through bills of materials, nets it against on-hand and on-order inventory, and offsets by lead time to produce timed purchase and work order suggestions.
Phantom BOM
A phantom BOM is a subassembly that exists in the bill of material for engineering clarity but is never stocked or built as its own order. Planning blows straight through it, passing demand directly to its components on the parent job.
BOM Explosion
BOM explosion is the step in which MRP expands each parent item's planned quantity into dependent component requirements using the bill of materials, quantity-per factors, scrap and yield allowances, and effectivity dates, level by level.
Go Deeper
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How to Set Up Phantom BOM Items in SyteLine
Step-by-step guide to setting up phantom BOM items in Infor SyteLine for simplified production planning, including item configuration, BOM explosion, and MRP behavior.
Working with Multi-Level BOM in a live environment? Our engineers do this every day - and our AI agents automate most of it.