Omnichannel Inventory Management: 4 Strategies for Accurate Availability

Omnichannel inventory management is the practice of treating inventory in every store, warehouse, and sales channel as one shared pool, so each channel sells only what the business can actually fulfill.

Many retailers call this unified inventory management.

Customers now move between a retailer's website, marketplaces, and stores, and they expect the availability they see to be right. Even small gaps between the system and the shelf lead to oversold orders, cancellations, and lost trust.

In this guide, we explain what omnichannel inventory management is, how it differs from single-channel inventory, where available to promise (ATP) fits in, and the common problems it solves. Then we cover four strategies to look for when choosing an OMS.

What is omnichannel inventory management?

Omnichannel inventory management connects inventory data from the ERP, warehouse management system (WMS), and point of sale (POS) into one view. From that view, the business decides how much of each product each channel can sell, which locations can fulfill it, and which units stay reserved for store shoppers.

The goal is not just visibility. It is a sellable number for each channel that the retailer can keep, whether the order ships from a warehouse, ships from a store, or is picked up in store. An order management system (OMS) calculates that number and syncs inventory updates to every channel in real time, so availability changes as soon as stock moves.

How it differs from single-channel inventory management

In single-channel retail, inventory is simple: one location, one count, one place to sell. The number on hand is close enough to the number you can sell.

In omnichannel retail, the same unit can be claimed by a website order, a marketplace order, a pickup order, and a walk-in shopper at the same time. The on-hand count is no longer the sellable count. Retailers need rules for reservations, store buffers, channel limits, and which locations take part in online fulfillment. Without those rules, every channel sells against the same raw number and oversells it.

How available to promise fits in

Available to promise is the calculation that turns an on-hand count into a sellable one. A typical online ATP starts with the quantity on hand and subtracts units already reserved for orders, a safety stock held back for walk-in customers, a threshold buffer for the channel, orders waiting to be routed, and inventory at locations that do not sell online.

For example, a store with 10 units on hand, 2 reserved for open orders, and a safety stock of 3 can promise 5 units online. Our guide to available to promise in retail walks through the calculation in detail.

Common omnichannel inventory management problems

Most omnichannel inventory problems come from one of four gaps. The first is overselling, when channels sell against on-hand counts instead of ATP. The second is stale data, when channels update in batches and the count has changed since the last update. Real-time sync closes that gap, but only if the number being synced is accurate. Our post on why real-time sync alone does not stop overselling covers this in more detail.

The third is empty shelves, when online orders take the units that walk-in shoppers expected to find. The fourth is inaccurate store counts, which usually start at receiving. We cover that in why receiving is where inventory accuracy is decided. The four strategies below address these gaps directly.

4 strategies for omnichannel inventory management

Here are four must-have omnichannel inventory management capabilities that keep availability accurate and fulfillment on track:

1. Calculating Inventory Availability Across Multiple Channels

Omnichannel retailers often sell across multiple channels, including their own eCommerce platforms, physical stores, and marketplaces like Amazon and Walmart. Each channel comes with unique requirements and challenges, particularly in omnichannel inventory management. Achieving accurate inventory allocation across these channels is important to avoid issues such as overselling, delayed fulfillment, or inventory imbalances.

For example, marketplaces like Amazon impose strict penalties for late deliveries or canceled orders. To mitigate this risk, retailers can set a higher inventory buffer in the form of "Threshold" for such channels so that sufficient stock is available to meet the marketplace's requirements and avoid penalties. This approach helps maintain good standing with marketplaces while promising reliable fulfillment for customers.

Another scenario involves selectively making certain products available on specific channels. Retailers may choose to keep newly launched or high-priority products exclusive to their own eCommerce to drive traffic and maximize profit margins.

Without the right OMS, managing inventory allocation across multiple channels can lead to overselling and fulfillment delays, causing disruptions in customer experience and operational efficiency.

To address these complexities in omnichannel inventory management, a robust OMS should offer:

•  Enable retailers to define channel-specific inventory threshold to account for varying stock requirements and avoid overselling.

•  Support suppressing specific products from selected channels, offering flexibility to sell or restrict items as needed.

•  Accurately calculate channel-wise ATP, taking into account inventory thresholds, and suppressed product so that customers only see realistic availability across all platforms.

Fig 1: Channel-Wise ATP Calculation

Result? Retailers sell across multiple channels with fewer oversold orders, better fulfillment accuracy, and less risk of marketplace penalties.

2. Suppressing Inventory for Specific Locations Not Participating in Online Selling

Omnichannel retailers often face situations where they need to temporarily suppress certain locations from participating in online sales and in-store fulfillment. This could be due to various reasons such as staff shortages, ongoing renovations, or technical disruptions. In such scenarios, all available inventory from these stores should be suppressed to prevent overselling and maintain accurate stock visibility across channels.

Another common scenario is during high-traffic periods, such as in-store events or holiday seasons. In these situations, store managers do not want to completely halt in-store operations but need to manage the fulfillment load for online orders to balance walk-in and online demand. Setting fulfillment limits based on the store's capacity becomes necessary to alleviate pressure without compromising in-store service. Fulfillment limits should not affect the ATP inventory because even if a store’s max capacity is reached, its inventory is still available to fulfill orders the next day.

Without the right OMS, balancing in-store and online needs becomes difficult, increasing the likelihood of overselling and operational bottlenecks. To address these complexities in omnichannel inventory management, a robust OMS should provide:

•  Allow store managers to temporarily stop participating in online sales, keeping their inventory suppressed from ATP calculations.

Fig 2: Enable/Disable Online Selling

•  Define daily order limits for each store to reduce fulfillment burdens during high-traffic periods.

•  Flexibility to set the fulfillment capacity to zero when pausing fulfillment of online orders or enable unlimited order fulfillment when the store is fully operational.

Fig 3: Fulfillment Limits

Result? Retailers can adapt to real-time circumstances and only sell online what they can fulfill.

3. Calculating Inventory Availability Based on Locations and Their Fulfillment Roles

Some smaller stores, especially those in high-traffic areas, may not have the capacity to handle the packing and shipping of online orders. These stores can still support BOPIS, which aligns closely with serving walk-in customers, requiring less operational effort and space. For such stores, contributing its inventory for only in-store pick-up is a practical way to participate in omnichannel fulfillment without overburdening their staff or resources.

Other locations, such as flagship stores that have the infrastructure can accommodate both shipping and BOPIS. Meanwhile, some stores that focus exclusively on serving walk-in customers can still act as backup locations for fulfillment, stepping in when inventory at primary fulfillment locations is depleted. Using these as a last resort helps meet customer demands without compromising the shopping experience.

Without the right OMS, calculating ATP based on locations with different fulfillment roles becomes challenging, leading to inefficiencies. To address these complexities in omnichannel inventory management, an advanced OMS should provide the flexibility to:

•  Display ATP inventory based on which stores participate in Ship From Store or BOPIS or both.

•  Configure certain stores as backup locations that participate in fulfillment of online orders only as the last resort. This means that inventory available at backup locations is suppressed from online sales but only considered during order routing as the last resort.

Fig 4: Assign Backup Locations

Result? Retailers can make the most of each store's strengths while balancing the demands of online and offline channels.

4. Suppressing Inventory of Products from a Channel or Location

Omnichannel retailers handle a broad product catalog with diverse attributes and fulfillment needs. In such a setup, managing product availability becomes important to align with business goals. Certain products should only be offered through specific fulfillment methods, such as in-store pick-up or shipping, depending on their characteristics.

For example, high-demand items or newly launched products are often better suited for in-store purchases rather than online shipping. This approach helps maintain stock levels for walk-in customers, who rely on in-store availability. To cater to online demand, these products can be shipped from warehouses instead of stores. However, offering in-store pick-up for these items is still a valuable option. Customers picking up orders act similarly to walk-ins, helping strike a balance between inventory preservation and meeting demand.

In contrast, bulky or heavy products may not be ideal for in-store pick-up but can still be shipped directly from stores for online orders. Similarly, products requiring customization should be suppressed from both in-store pick-up and shipping, as they are best fulfilled at specialized locations such as warehouses or workshops.

Without the right OMS, suppressing specific products from specific locations can become complex. Retailers may inadvertently allow unsuitable fulfillment options, leading to customer dissatisfaction, logistical issues, or inventory shortages. For example, allowing pick-up for heavy items unsuitable for transportation can create unnecessary logistical bottlenecks.

To overcome these issues in omnichannel inventory management, an advanced OMS should calculate ATP based on rules like:

•  Allow a product to be picked up from the store while suppressing it for Ship From Store at specific locations.

Fig 5: Allowing In-Store Pick-Up Only

•  Allow a product to be shipped from the store while suppressing it for store pick-up at specific locations.

Fig 6: Allowing Ship From Store Only

•  Calculate ATP by entirely suppressing a product’s inventory from specific locations for all fulfillment methods.

Fig 7: Suppress Product Fulfillment From Stores

Result? Customers see only valid fulfillment options, reducing errors and enhancing the overall shopping experience.

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Addressing the complexities of omnichannel inventory management requires more than traditional systems. Accurate channel-wise ATP calculations, supported by a robust OMS, empower retailers to manage diverse inventory needs across channels and product lines.

HotWax Commerce OMS offers capabilities such as channel-wise ATP calculations, suppressing non-participating locations, role-based fulfillment configurations, and suppressing specific products. Complemented by a dedicated ATP App, it gives retailers one place to manage omnichannel inventory rules, so availability stays accurate and overselling and underselling become rare.

For the principles behind these strategies, read our overview of the principles of omnichannel inventory management, and learn how HotWax Commerce delivers unified inventory across every channel.

Contact an expert to see how HotWax Commerce OMS can help you in achieving effective omnichannel inventory management.

Frequently asked questions about omnichannel inventory management