Indented Bill of Material
Definition
An indented bill of material is a multilevel BOM display that shows the product structure hierarchically, indenting each level so parents, subassemblies, and components appear in their true structural relationships.
In Practice
The indented format is how humans read what MRP processes: level 0 is the finished item at the left margin, level 1 subassemblies indent one step, their level 2 components indent further, and so on to purchased parts. A pump assembly might show the motor subassembly at level 1, its rotor at level 2, and the rotor's shaft and laminations at level 3, each with quantity per parent.
Planners use indented BOMs to trace cost roll-ups, find every level a change affects, and understand lead-time stacking — the critical path of a product is visible by walking the longest chain of indents. The mirror image is the indented where-used report, which walks upward from a component to every parent that consumes it.
Frequently Asked Questions
What is the difference between an indented and a single-level BOM?
A single-level BOM lists only an item's immediate components — one parent, one level down. An indented BOM expands the full structure through every level, using indentation to show hierarchy from finished product to purchased parts. The single-level view is modular for maintenance; the indented view shows the whole tree.
How do you read an indented bill of material?
Left margin is the end item (level 0); each indentation step goes one level deeper into the structure. A level 2 item belongs to the level 1 item directly above it. Quantities are per parent, so extended requirements multiply down the chain — 2 per parent under 3 per grandparent means 6 per end unit.
Related Terms
A multilevel bill of material is the complete product structure showing every level of assembly — from the finished item through subassemblies down to purchased components and raw materials — with quantities linking each parent to its children.
Single-Level Bill of MaterialA single-level bill of material lists only an item's immediate components — one level down — with quantities per parent, serving as the building block from which multilevel product structures are assembled.
Low-Level CodeA low-level code is a number assigned to each item identifying the lowest level at which it appears in any bill of material, used by MRP to ensure an item's requirements are fully accumulated before its needs are calculated.
Where-Used ListA where-used list is a report showing every parent assembly and product in which a given component appears, tracing the bill of material upward — the reverse of a BOM explosion.