---
title: "Bill of Materials (BOM): Advantages, Structure, Types & Content"
description: "Find out what a bill of materials is, its advantages, who uses it, structure of BOM, content of BOM, types of bills of material, and effective BOM management."
canonical: "https://busy.in/inventory-guide/what-is-the-bill-of-materials-bom/"
author: "Jagdish Prasad"
published: "2023-05-05T08:30:00.000Z"
category: "Inventory Guide"
---

-   A Bill of Materials is the master list of materials, parts, quantities, and instructions required to manufacture a product.
-   A single-level BOM works for simple products, while a multi-level BOM is better for products with sub-assemblies.
-   Common BOM types include manufacturing BOM, engineering BOM, sales BOM, configurable BOM, service BOM, phantom BOM, and software BOM.
-   A BOM helps businesses plan purchases, control inventory, calculate product cost, reduce wastage, and avoid production delays.
-   For Indian manufacturers, BOM records can support GST-ready item masters, HSN mapping, job work tracking, and [**ITC reconciliation**](https://busy.in/gst/reconciliation-under-gst/) , but they do not replace statutory GST documents.
-   BOM should be managed with version control, change approval, accurate quantities, standard units of measurement, and regular production audits.

# What is a Bill of Materials (BOM)? Meaning, Types, Format and Example

## **What is a Bill of Materials?**

A Bill of Materials is a structured document that lists all inputs required to manufacture, assemble, or maintain a product. These inputs may include raw materials, bought-out components, sub-assemblies, consumables, packaging material, and sometimes assembly instructions.

For example, if a business manufactures a wooden chair, the BOM may include wooden planks, chair legs, screws, adhesive, varnish, packaging material, and labour or process notes. If the chair has separate seat, frame, and backrest assemblies, the BOM can also show how each sub-assembly is made.

Basically, a good BOM removes guesswork from manufacturing. It creates a common reference for everyone involved in making the product and is used by multiple teams:

| Team | How They Use the BOM |
| --- | --- |
| Purchase Team | To know what materials must be ordered |
| Production Team | To know what items are needed for each production run |
| Inventory Team | To reserve, issue, and track stock |
| Finance Team | To calculate product cost and margin |
| Quality Team | To verify whether the right parts were used |
| Sales Team | To understand kits, bundles, or configurable products |

## **Why is a BOM Important in Manufacturing?**

A BOM is important in manufacturing because it gives every team a clear list of the materials, components, and quantities required to make a finished product. It helps the purchasing team know exactly what to buy and in what quantity. For example, if one finished product needs 4 bolts, a production plan for 500 units will require 2,000 bolts before considering wastage or safety stock.

When a BOM is linked with [**inventory software**](https://busy.in/accounting-software/inventory-management/) or ERP, the business can check raw material availability before accepting or starting a production plan. This reduces last-minute shortages, emergency purchases, and production delays. It also helps calculate the material cost of a finished product, so if the price of a key raw material increases, the business can quickly understand its impact on the final product cost.

A BOM also reduces wastage and production errors because the production team follows a standard material list. This lowers the chances of over-issuing materials, using the wrong component, or missing an important part. For products with quality issues, a BOM supports traceability by helping identify which component, supplier, batch, or sub-assembly may have caused the problem, especially in industries such as electronics, machinery, food processing, automotive parts, and pharma-related manufacturing.

## **What Does a BOM Include?**

A BOM should contain enough detail for all the relevant teams to use it without confusion. A common mistake is to create a BOM with only material names and quantities. That may work at a very small scale, but as production grows, more specific fields become essential. Check the full list below:

| BOM Field | Meaning | Example |
| --- | --- | --- |
| Finished Product Name | Name of the final item being manufactured | Wooden Chair |
| BOM Level | Position of an item in the product hierarchy | Level 0, Level 1, Level 2 |
| Item Code or Part Number | Unique code for each material or component | WC-BOLT-M8 |
| Item Name | Name of the raw material or component | M8 Bolt |
| Description | Size, grade, material, colour, or specification | Stainless steel bolt, 30 mm |
| Quantity | Quantity required per finished unit | 8 |
| Unit of Measurement | Measurement unit used for the item | Pcs, kg, metre, litre |
| Procurement Type | Whether the item is bought or made internally | Buy or Make |
| Scrap or Wastage % | Expected process loss, if applicable | 2% |
| Supplier Details | Approved supplier or alternate supplier | Supplier A |
| Lead Time | Time required to procure or make the item | 7 days |
| [**Unit Cost**](https://busy.in/accounting/marginal-cost-in-accounting-formula-examples-and-business-use/) | Cost per unit for costing calculation | ₹4 per piece |
| Revision Number | BOM version or change record | Rev A1 |
| Notes | Special instructions or substitutes | Use Supplier B if Supplier A is unavailable |

## **Single-Level BOM vs Multi-Level BOM**

### **Single-Level BOM**

A single-level BOM lists all components required to make the finished product in one flat list. It does not show parent-child relationships between sub-assemblies. This works well for simple products such as a basic packaged kit, small furniture item, or simple assembled product with very few parts. But its limitation is that it does not clearly show which components belong to which sub-assembly. So, if the product becomes complex, a flat BOM becomes difficult to manage.

**Example:**

| Finished Product | Component | Quantity |
| --- | --- | --- |
| Wooden Chair | Wooden Seat | 1 |
| Wooden Chair | Chair Legs | 4 |
| Wooden Chair | Screws | 8 |
| Wooden Chair | Varnish | 0.25 litre |

### **Multi-Level BOM**

A multi-level BOM shows the full structure of a product. It starts with the finished product and then breaks it down into sub-assemblies, components, and raw materials. A multi-level BOM is better for products with multiple sub-assemblies because it helps with costing, material planning, [**quality checks**](https://busy.in/accounting/auditing-accounting-objectives-procedures-and-types/) , and defect tracing.

**Example:**

| Level | Item | Quantity |
| --- | --- | --- |
| 0 | Wooden Chair | 1 |
| 1 | Seat Assembly | 1 |
| 2 | Wooden Seat Panel | 1 |
| 2 | Varnish | 0.25 litre |
| 1 | Leg Assembly | 4 |
| 2 | Wooden Leg | 4 |
| 2 | Floor Cap | 4 |
| 1 | Hardware Kit | 1 |
| 2 | Screws | 8 |
| 2 | Washers | 8 |

## **Bill of Materials Example**

Here is a BOM example for manufacturing one wooden chair. This type of BOM helps the manufacturer calculate material requirements for any production quantity. If the business wants to produce 100 chairs, the system can multiply the material requirement automatically and check stock availability from the BOM given below.

| Level | Item Code | Item Name | Qty | UOM | HSN Code | GST | Procurement | Unit Cost (Net) | Gross Qty (with Wastage) | Total Cost |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 0 | WC-FG-001 | Wooden Chair | 1 | Pcs | 9401 | 18% | Make | \- | 1 | \- |
| 1 | WC-SEAT-001 | Seat Assembly | 1 | Pcs | \- | \- | Make | \- | 1 | \- |
| 2 | WC-PLANK-001 | Teak Wood Seat Panel | 1 | Pcs | 4407 | 12% | Buy | ₹320 | 1.05 | ₹336 |
| 2 | WC-VARN-001 | Wood Varnish | 250 | Ml | 3208 | 18% | Buy | ₹280/L | 270 | ₹75.6 |
| 1 | WC-LEG-ASM | Leg Assembly | 4 | Pcs | \- | \- | Make | \- | 4 | \- |
| 2 | WC-LEG-045 | Teak Wood Leg | 4 | Pcs | 4407 | 12% | Buy | ₹180 | 4.2 | ₹756 |
| 2 | WC-CAP-001 | Floor Cap | 4 | Pcs | 3926 | 18% | Buy | ₹12 | 4 | ₹48 |
| 1 | WC-HW-KIT | Hardware Kit | 1 | Set | 7318 | 18% | Make | \- | 1 | \- |
| 2 | WC-BOLT-M8 | M8 Bolt | 8 | Pcs | 7318 | 18% | Buy | ₹4 | 8 | ₹32 |
| 2 | WC-WASH-M8 | Washer | 8 | Pcs | 7318 | 18% | Buy | ₹1.50 | 8 | ₹12 |

## BOM vs BOQ vs Work Order vs Production Order

These terms are often confused, but they are not the same. A BOM is the product recipe. A production order tells the factory how many units to make. A work order breaks that production into actual tasks. A BOQ is more common in [**project-based industries**](https://busy.in/accounting/project-accounting-tracking-costs-budgeting-and-profitability/) such as construction. Check the table for a comparative analysis:

| Term | Meaning | Used For |
| --- | --- | --- |
| BOM | List of materials and components required to make a product | Manufacturing and assembly |
| BOQ | Bill of Quantities used to estimate work, materials, and costs in projects | Construction, contracts, civil work |
| Production Order | Instruction to manufacture a specific quantity of finished goods | [**Production planning**](https://busy.in/accounting/erp-vs-accounting-software/) |
| Work Order | Task-level instruction for a workstation, operator, or department | Shop-floor execution |

## **How to Create a Bill of Materials**

### **Step 1: Define the finished product**

Start with the finished item name, item code, unit of measurement, and product description. This becomes Level 0 in the BOM.

### **Step 2: Break the product into sub-assemblies**

Identify the major sections of the product. For example, a chair may have seat assembly, leg assembly, backrest assembly, and hardware kit.

### **Step 3: List all components under each sub-assembly**

Add every raw material, bought-out part, consumable, and packaging material. Do not ignore small items such as screws, labels, adhesives, tapes, washers, or cartons because they affect cost and production readiness.

### **Step 4: Add accurate quantities and UOM**

Use standard units such as pieces, kg, metre, litre, box, roll, or set. Avoid mixing units in the same BOM. For example, do not use grams in one line and kg in another unless the conversion is clearly defined.

### **Step 5: Define Buy or Make**

Mark whether each item is purchased from a supplier or manufactured internally. Items marked as “Make” may need their own child BOM.

### **Step 6: Add costing and supplier details**

Add unit cost, supplier name, alternate supplier, purchase lead time, and expected wastage. This helps both costing and procurement.

### **Step 7: Review with all relevant teams**

Before approving the BOM, review it with production, purchase, inventory, quality, and finance teams. This reduces the chances of practical shop-floor issues later.

### **Step 8: Assign revision control**

Every approved BOM should have a version number. When any material, quantity, supplier, or process changes, the BOM should be updated through a controlled process.

## **BOM Management Best Practices**

### **Maintain one source of truth**

A BOM should not exist in multiple uncontrolled spreadsheets. If different teams use different versions, errors are almost guaranteed. Ideally, BOMs should be maintained in ERP or inventory software where item masters, stock, [**purchase orders**](https://busy.in/accounting/accounts-payable-explained-meaning-process-and-how-to-manage-it-better/) , and production orders are connected.

### **Keep item codes consistent**

Every raw material, component, sub-assembly, and finished good should have a unique item code. Duplicate names such as “bolt”, “small bolt”, and “steel bolt” create confusion during purchase and stock issue.

### **Add approved substitutes**

For critical components, mention approved alternate items or suppliers. This helps production continue when the primary item is unavailable, without allowing random substitution.

### **Include wastage where it is real**

Many industries have normal process loss. Furniture may have cutting wastage, food manufacturing may have yield loss, and metal fabrication may have scrap. The BOM should capture realistic wastage instead of assuming perfect consumption.

### **Audit BOMs against actual production**

A BOM should not remain theoretical. Compare standard BOM consumption with actual material issue and actual output. If workers regularly consume more or less material than the BOM, investigate the reason and update the BOM if needed.

### **Keep engineering and manufacturing changes controlled**

Small changes can create large production problems. If a part number, design, quantity, grade, or supplier changes, the change should be reviewed and approved before production starts using the new BOM.

## **BOM Accuracy and Version Control**

BOM accuracy means the BOM correctly reflects the materials, quantities, units, part numbers, and processes actually required to manufacture the product. Many manufacturers use 98%+ BOM accuracy as an internal target for reliable MRP and production planning. However, this should be treated as an operational benchmark, not a statutory or universal official standard.

Version control is equally important. This is because old products may still be under warranty, audit, recall, repair, or customer complaint review. Deleting old BOM versions can create traceability problems later. A BOM should show: current revision number, date of change, person who made the change, reason for change, approval status, effective date from which the new BOM applies, and version archive for reference.

## **BOM and GST Compliance in India**

A BOM is not a [**GST return**](https://busy.in/gst/gst-returns/) , tax invoice, e-invoice, e-way bill, or statutory filing by itself. However, for Indian manufacturers, it can support better GST-ready records when connected with item masters, inventory, purchase, production, and job work records.

### **BOM and Input Tax Credit**

A BOM supports ITC reconciliation by showing which inputs are expected to be used in manufacturing. However, ITC eligibility still depends on GST law conditions, purchase invoices, supplier reporting, receipt records, GSTR-2B, GSTR-3B, and other applicable compliance requirements.

### **HSN Code Mapping**

Manufacturers should maintain correct [**HSN codes**](https://busy.in/hsn/) in the item master for raw materials, components, and finished goods. HSN mapping helps apply the correct GST rate, prepare invoices correctly, and reduce classification errors. For rate validation, businesses should refer to the [**CBIC GST Goods and Services Rates**](https://cbic-gst.gov.in/gst-goods-services-rates.html) .

### **BOM and Job Work**

If materials are sent to a job worker, the BOM can help track what inputs were sent, what process was performed, and what quantity was received back. Under GST, the movement of goods for job work can be documented through delivery challan under [Rule 55](https://taxinformation.cbic.gov.in/content/html/tax_repository/gst/rules/cgst_rules/active/chapter6/rule55_v1.00.html) , which includes details such as challan number, GSTIN details, HSN, quantity, taxable value, place of supply for inter-state movement, and signature.

For ITC on goods sent for job work, [Section 19](https://taxinformation.cbic.gov.in/content/html/tax_repository/gst/acts/2017_CGST_act/active/chapter5/section19_v1.00.html) allows credit on [**inputs and capital goods**](https://busy.in/gst/input-tax-credit-on-capital-goods/) sent to a job worker, subject to conditions. Inputs should generally be returned or supplied from the job worker’s premises within 1 year, while capital goods have a 3-year period. Moulds, dies, jigs, fixtures, and tools are treated separately.

### **BOM and ITC-04**

Form GST ITC-04 is used to report details of inputs or capital goods sent to and received from job workers. The GST portal manual states that, from 1 October 2021, ITC-04 is filed half-yearly for taxpayers with an [**annual aggregate turnover**](https://busy.in/gst/minimum-turnover-for-gst-registration-in-india/) above ₹5 crore, and yearly for taxpayers with an annual aggregate turnover up to ₹5 crore, effective from FY 2022-23. A good BOM does not replace ITC-04, but it helps maintain cleaner job work records.

### **BOM and E-Invoicing**

E-invoicing is not generated from the BOM directly. It is invoice-level compliance. However, BOM-linked item masters can help ensure that item descriptions, HSN codes, units, [**taxable values**](https://busy.in/gst/value-of-supply-under-gst/) , and GST rates are correct in sales and dispatch records.

The official [**e-invoice portal**](https://busy.in/gst/invoice-registration-portal-irp-under-gst/) lists the notified AATO rollout dates, including ₹5 crore to ₹10 crore from 01-08-2023, with less than ₹5 crore optional. It also clarifies that portal enablement is solely for facilitation, and the legal obligation depends on the conditions prescribed under Rule 48(4).

## **Conclusion**

A Bill of Materials is much more than a list of raw materials. It connects product design, purchase planning, inventory control, production, costing, quality checks, and [**compliance records**](https://busy.in/accounting/gst-compliant-bookkeeping-best-practices/) .

For a small manufacturer, even a simple BOM can reduce confusion and improve material planning. For a growing business, a well-maintained multi-level BOM can prevent stockouts, reduce waste, improve costing accuracy, and improve coordination between teams.

The most important point is accuracy. A BOM should be reviewed, version-controlled, and regularly compared with actual production consumption. For Indian manufacturers, BOM records should also be aligned with GST-ready item masters, HSN codes, [**job work**](https://busy.in/gst/all-about-input-tax-credit-on-job-work/) challans, and inventory movements.

Manage materials, production, inventory, and [**GST-ready records**](https://busy.in/accounting/gst-ready-accounting-software-features/) more accurately with BUSY [**accounting software**.](https://busy.in/accounting-software/) Book a free demo today.

## About the author

**Jagdish Prasad**

Jagdish Prasad is a Chartered Accountant with over 5 years of experience. He helps people and businesses with GST, income tax, and HSN codes. Jagdish makes sure his clients follow all tax rules and save money the right way. He also enjoys writing simple articles to help others understand taxes and stay updated with the latest rules.

## Frequently asked questions

### What is the full form of BOM?

BOM stands for Bill of Materials. It is a structured list of raw materials, components, sub-assemblies, quantities, and instructions required to manufacture or assemble a product.

### Is a BOM only used in manufacturing?

No. BOMs are mainly used in manufacturing, but similar structures are also used in software, maintenance, engineering, product kits, and service operations. For example, a Software BOM lists software components, while a Service BOM lists spare parts needed for repair.

### What is the difference between BOM and BOQ?

A BOM is used to define the materials and components needed to manufacture a product. A BOQ, or Bill of Quantities, is commonly used in construction and project work to estimate quantities, materials, labour, and costs for a project.

### What is the difference between BOM and recipe?

A recipe is usually used in food, chemical, pharma, or process manufacturing, where ingredients are mixed or processed. A BOM is broader and is used for discrete manufacturing, assembly, kits, machinery, electronics, furniture, and other products.

### Can a BOM include labour cost?

A basic BOM usually lists materials and components. Labour and machine costs are often captured through routing, production cost sheets, or overhead allocation. However, some businesses include labour cost references in an extended BOM for internal costing.

### Should packaging material be included in a BOM?

Yes, if packaging is part of the finished product cost or required for dispatch. Boxes, labels, pouches, inserts, tapes, and cartons should be included where they affect costing, stock planning, or production readiness.

### Can BOM help reduce dead stock?

Yes. A BOM helps identify which raw materials are linked to which finished products. If a component is no longer used in any active BOM, the business can flag it as slow-moving, obsolete, or excess stock.

### Does GST require every manufacturer to maintain a BOM?

GST law does not require every business to maintain a BOM in a specific format. However, for manufacturers, BOM records can support inventory tracking, job work reconciliation, costing, HSN mapping, and ITC review. Statutory GST compliance still depends on invoices, returns, challans, e-way bills, e-invoices where applicable, and other prescribed documents.

### Can a BOM be changed after production starts?

It can be changed, but not casually. Any change in material, quantity, supplier, item code, or process should go through approval and version control. Otherwise, purchase, production, and costing teams may work from different assumptions.

### What is the best software for BOM management?

The best software depends on the size and complexity of the business. Small businesses may start with spreadsheets, but manufacturers with regular production, inventory, purchase, job work, and GST needs should use accounting or ERP software that connects BOM with stock, purchase, production, and financial records.

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