# Multi-Level BOM

> Source: https://netray.co/glossary/multi-level-bom
> Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems.
> Section: Glossary

## Short answer

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.

## Aliases

- indented BOM
- multilevel bill of materials
- BOM levels

## Category

manufacturing

## Full Definition

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.

## Faq

### What is the difference between a single-level and multi-level BOM?

**Answer:** 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?

**Answer:** 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?

**Answer:** 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.

## Search terms

multi-level BOM, indented BOM, BOM levels, low level code, single level vs multi level BOM, multilevel bill of materials

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