Optimize Inventory Flow with Phantom BoMs and Subassemblies in Odoo 18

In today’s fast-moving manufacturing and supply chain environment, businesses need to stay agile. Odoo 18 introduces powerful tools to streamline production processes—two of the most impactful being Phantom Bills of Materials (BoMs) and subassemblies. For manufacturers looking to reduce inventory clutter, cut lead times, and simplify production management, mastering the use of Odoo phantom BoMs is essential.

In this post, we’ll explore what phantom BoMs and subassemblies are, when to use them, and how Odoo 18 makes it easier than ever to optimize your inventory and streamline operations in 2025.

What Are Phantom BoMs in Odoo 18?

A Phantom Bill of Materials is a special type of BoM in Odoo used for virtual or non-stocked assemblies. Unlike a traditional BoM, a phantom BoM is not manufactured or stored as a separate item. Instead, its components are consumed directly during the production of the final product.

Key Characteristics of Phantom BoMs:
✅ On-the-fly assembly – Components are pulled and used at production time.
✅No stock of the subassembly is recorded.
✅Ideal for temporary, once-use assemblies or kits.
✅ Streamlined multi-level BoMs into a single production operation.

Use Case Example:
Let’s say you manufacture a computer system that includes a CPU subassembly (motherboard + processor + RAM). Instead of manufacturing and stocking the CPU module separately, you can set the CPU’s BoM as a phantom. This way, during the assembly of the final computer product, Odoo will consume the raw components (motherboard, processor, RAM) directly.

New Enhancements for Phantom BoMs in Odoo 18 (2025 Update)

Odoo 18 refines the functionality of phantom BoMs, giving operations even more control and efficiency in manufacturing setups.

Notable 2025 Enhancements:
✅ Visual BoM Trees: Easily map product hierarchies at every stage.
✅ Improved Routing Integration: Phantom BoMs now support multi-step routing, allowing you to better simulate lead times and work-center operations even for virtual assemblies.
✅ Real-time Component Allocation: Better support for demand-driven manufacturing by allocating Phantom BoM components directly from available stock across multiple warehouses.
✅ Subassembly Tracking in MRP Orders: Even though phantom subassemblies aren’t stocked, Odoo 18 now allows visual tracking of their components through the master production order.

These improvements make it easier for business decision-makers to design more efficient production workflows without overcomplicating your master data or inventory logic.

Understanding Subassemblies in Odoo 18

While phantom BoMs deal with non-stocked assemblies, subassemblies refer to components that are manufactured separately and then used as part of a parent product.

When to Use Subassemblies:
✅ When an intermediate product is reused in multiple finished products.
✅ When lead times for the subassembly require pre-production.
✅ When separate quality checks, routing, or production timelines apply.

Subassemblies vs. Phantom BoMs

Feature	Subassembly	Phantom BoM
Stocked	Yes	No
Routing	Separate work order	Inherited from parent
Lead Time	Considered independently	Not tracked independently
Complexity	Higher	Lower

Odoo 18 allows both strategies to coexist, and in some cases, using a hybrid approach—phantom BoMs for disposable or unique kits, and subassemblies for complex parts—can provide the best efficiency.

Best Practices for Using Phantom BoMs and Subassemblies Effectively

Let’s break down the recommended workflow for optimizing inventory flow and production runs using these tools in Odoo 18.

1. Identify Components Suitable for Phantom BoMs
Start by conducting a product structure audit. Look for:
✅ Repetitive kits that don’t require separate stock management.
✅Temporary or client-specific assemblies (e.g., promotional bundles).
✅Items that add complexity to your stock levels without real need.

2. Configure Your Phantom BoMs in Odoo
To set up a Phantom BoM in Odoo 18:
✅ Go to your product.
✅Create a new Bill of Materials.
✅Set the BoM Type to “Phantom”.
✅Assign routing only if production steps still apply under the parent order.

When manufacturing the parent, Odoo will automatically pull components listed in the phantom BoM from stock and include them in the operation.

3. Leverage Subassemblies for Reusable Modules

If you have components that are part of multiple final products (motors, electronics modules, PCBs), it’s best to make these subassemblies. Maintain stock visibility, allow for independent production, and recycle them across builds.

Use multi-level BoMs and create routing rules independently for subassemblies to align with shop floor operations and lean manufacturing.

4. Monitor Real-time Inventory Movement

Odoo 18’s dynamic inventory planner lets you visualize the flow of phantom and subassembly components across multiple manufacturing orders in real time. Use this to keep tight control over component availability and avoid production slowdowns.

5. Train Your Team

Ensure your production planners, warehouse managers, and procurement officers understand the difference between phantom and traditional subassemblies. Align purchasing, routing, and manufacturing accordingly.

Benefits of Using Odoo Phantom BoMs in 2025

As manufacturers face increasing complexity, rising material costs, and shorter delivery windows in 2025, adopting phantom BoMs helps businesses:

✅ Reduce inventory levels
✅ Accelerate order fulfillment
✅ Simplify BoM structures
✅ Decrease planning errors
✅ Improve MRP responsiveness
✅ Lower operational overhead

Odoo 18, with its improved Manufacturing and Inventory modules, is built to support these modern workflows, making it a robust ERP platform for manufacturers scaling their operations without introducing inefficiencies.

Real-World Example: Streamlining Complex Kit Operations

One of our clients in the consumer electronics space recently migrated from a tiered traditional BoM system to a hybrid model using phantom BoMs in Odoo 18. By converting low-complexity kits to phantom BoMs and keeping complex circuitry modules as subassemblies, they:

✅ Reduced picking lists by 32%
✅ Improved stock rotation
✅ Cut average assembly time by 18%
✅ Decreased backorders due to clearer component demand planning

This is a blueprint any medium to large manufacturer can replicate for better growth agility.

Final Thoughts

Whether you’re managing a multi-product line or scaling a custom on-demand production facility, utilizing Odoo phantom BoMs and subassemblies strategically can greatly streamline your workflow. With Odoo 18’s enhancements, it’s easier than ever to simplify operations while improving production speed and accuracy.

Phantom BoMs enable faster, leaner, and more cost-effective manufacturing. Odoo 18 brings this functionality to the forefront with better integration, smarter routing, and adaptive inventory control—all crucial for succeeding in 2025’s competitive landscape.