Bill of Materials (BOM)

A bill of materials (BOM) is a structured list of every material, component, and quantity required to complete a specific job, build, or project. For project-based businesses - AV integrators, electrical contractors, furniture dealers, and promotional merchandise distributors - the BOM translates what has been quoted into exactly what needs to be purchased. A BOM with gaps or errors leads directly to emergency procurement, job delays, and margin loss.

What a Bill of Materials Contains

A BOM lists every item needed for the job along with the quantity, unit of measure, specification, and intended supplier. For an AV system installation, the BOM might include display screens by model number, cabling by meter run, rack components by unit, and control system hardware. For a promotional merchandise order, it covers the blank goods by SKU and colorway, decoration consumables by method, and packaging materials. For a construction fit-out, it lists timber sections by dimension, fixings by type and count, and plasterboard by sheet count.

Each BOM line should be specific enough to raise a purchase order directly from it. Vague entries like "cabling - various" create ambiguity that results in wrong items ordered and job delays. A well-structured BOM includes the supplier reference or product code alongside the quantity so that procurement can act without returning to the estimator for clarification.

How the BOM Drives Procurement and Job Costing

The BOM connects three processes. At the quoting stage, it drives cost calculation - each line is priced to build up the total job cost before margin is applied. When the job is won, the BOM becomes the procurement trigger: each line generates a purchase order to the relevant supplier. During job execution, the BOM provides the baseline against which delivery notes and supplier invoices are matched.

BOM accuracy is commercially important. An omission at quoting means a cost arrives with no corresponding quote line and has to be absorbed. Small missing items - a cable tray run, a consumables allowance, a set of hardware fixings - rarely justify a variation order but collectively erode job margin by 3-8%. Specification errors carry a different risk: a line that reads "cable tray - 3m lengths" without the width, material grade, and finish code can result in the wrong product being delivered, a return and re-order delay, and a restocking fee.

The discipline fix is to populate the BOM from the survey or specification document rather than from memory or a previous job's materials list. Each item should be traceable back to a drawing reference, a measurement, or a specification clause.

Zigaflow links quote line items directly to purchase orders when a job is confirmed, so the BOM built at the quoting stage becomes the procurement list without rekeying. That connection reduces the gap between what was priced and what was actually ordered.