Multi-Warehouse Inventory

Overview

Multi-warehouse inventory lets you stock products at multiple physical locations — warehouses, stores, 3PLs — and route each order to the location best positioned to fulfill it. Shopify and BigCommerce have multi-location inventory built in. WooCommerce needs a plugin. Only build a custom allocation engine if your routing logic (zone-based, cost-optimized, split fulfillment) exceeds what platform tools support.

When to Use This Skill

When a merchant operates more than one warehouse, store, or 3PL (third-party logistics) provider
When shipping cost is significant and routing orders from the nearest warehouse matters
When stock imbalance between locations requires transfer orders to redistribute inventory
When orders must sometimes be split across two warehouses because no single location has all items

Core Instructions

Step 1: Determine platform and choose the right tool

Platform	Built-in Multi-Location	Recommended Extension
Shopify	Yes — up to 1,000 locations (Basic: 4, Shopify plan: 5, Advanced: 8)	ShipBob or Flexport for 3PL fulfillment routing; ShipHero for advanced routing rules
WooCommerce	No — requires a plugin	ATUM Multi-Inventory (add-on) or WooCommerce Multi-Location Inventory by Iconic
BigCommerce	Yes — Multi-Location Inventory app (free)	ShipStation for advanced routing; Whiplash or ShipBob for 3PL integration
Custom / Headless	Build allocation engine with proximity-first routing	Required when no platform tools meet routing and split-fulfillment requirements

Step 2: Platform-specific setup

Shopify

Shopify has native multi-location inventory.

Set up locations:

Go to Settings → Locations → Add location
Add each warehouse, store, or fulfillment center
Enter the address (used for shipping rate calculation)
Assign products to each location — go to a product, click a variant, and set the quantity at each location

Configure fulfillment routing:

Go to Settings → Shipping and delivery → Shipping
Under Fulfillment from, set the priority order for your locations
Shopify routes orders to the first location in your priority list that has stock for all items
For more sophisticated routing (proximity-based, cost-optimized): install ShipHero or ShipBob from the App Store

Transfer orders between locations:

Go to Inventory → Transfers → Create transfer
Select the Origin location (where stock is coming from)
Select the Destination location
Add the products and quantities to transfer
When goods arrive, go to Transfers → [Transfer] → Accept items — Shopify automatically increments the destination and decrements the origin

3PL integration:

For ShipBob: Install ShipBob from the App Store; ShipBob pulls orders from Shopify and routes to the nearest fulfillment center automatically
For Flexport: Install the Flexport app; products and inventory sync bi-directionally

WooCommerce

WooCommerce requires a plugin for multi-location inventory.

Option A: ATUM Multi-Inventory (recommended)

Install ATUM Inventory Management for WooCommerce (free core) + ATUM Multi-Inventory add-on (paid)
In ATUM, go to Multi-Inventory → Locations → Add Location
For each product, go to the ATUM Multi-Inventory tab and assign quantities per location
Configure inventory selection rule (region-based, priority-based, or first-available)

Option B: WooCommerce Multi-Location Inventory by Iconic

Install the plugin
Go to WooCommerce → Multi-Location Inventory → Locations and add your warehouses
Edit each product and set per-location stock quantities
Configure fulfillment routing in the plugin settings

Transfer orders:

ATUM Multi-Inventory includes a transfer order feature — go to ATUM → Inventory Transfers → New Transfer
Set origin, destination, products, and quantities
Mark as received to update stock automatically

BigCommerce

BigCommerce supports multi-location inventory via a free app.

Enable Multi-Location Inventory:

Go to Apps → Search "Multi-Location Inventory"
Install and launch the app
Add locations: Locations → Add location with name and address
Assign stock per product per location

Configure fulfillment routing:

In the Multi-Location Inventory app, go to Routing Rules
Set rules: ship from nearest, ship from cheapest, ship from location with most stock, etc.
BigCommerce generates split shipments automatically when an order can't be fulfilled from a single location

For 3PL integration:

Install ShipStation from the BigCommerce App Marketplace
ShipStation connects to your 3PL providers and routes based on your rules

Custom / Headless

For headless storefronts, build an allocation engine that selects the best location(s) for each order:

// lib/allocation.ts
import { haversineDistance } from './geo';

interface OrderItem { variantId: string; quantity: number; productName: string; }
interface AllocationResult {
  type: 'single' | 'split';
  fulfillments: { locationId: string; items: OrderItem[] }[];
}

export async function allocateOrder(orderItems: OrderItem[], shippingAddress: Address): Promise<AllocationResult> {
  const locations = await db.locations.findMany({ where: { active: true } });

  // Fetch inventory availability for all required variants at all locations
  const inventory = await db.inventoryLevels.findMany({
    where: { variantId: { in: orderItems.map(i => i.variantId) } },
  });
  const invMap = buildInventoryMap(inventory); // locationId -> variantId -> available

  // Score locations by distance to shipping address (proximity-first routing)
  const scored = locations
    .map(loc => ({
      ...loc,
      distanceKm: haversineDistance({ lat: loc.lat, lng: loc.lng }, { lat: shippingAddress.lat, lng: shippingAddress.lng }),
    }))
    .sort((a, b) => a.distanceKm - b.distanceKm);

  // Prefer single-location fulfillment to avoid split shipments
  for (const location of scored) {
    const canFulfillAll = orderItems.every(item => (invMap[location.id]?.[item.variantId] ?? 0) >= item.quantity);
    if (canFulfillAll) return { type: 'single', fulfillments: [{ locationId: location.id, items: orderItems }] };
  }

  // Fall back to split fulfillment — greedy assignment to nearest location with stock
  const remaining = [...orderItems];
  const fulfillments: AllocationResult['fulfillments'] = [];

  for (const location of scored) {
    const canFulfill = remaining.filter(item => (invMap[location.id]?.[item.variantId] ?? 0) >= item.quantity);
    if (canFulfill.length > 0) {
      fulfillments.push({ locationId: location.id, items: canFulfill });
      canFulfill.forEach(item => remaining.splice(remaining.findIndex(r => r.variantId === item.variantId), 1));
    }
    if (remaining.length === 0) break;
  }

  if (remaining.length > 0) throw new Error('Cannot fulfill order — insufficient stock across all locations');
  return { type: 'split', fulfillments };
}

// Transfer order management
export async function receiveTransferOrder(transferOrderId: string, receivedItems: { variantId: string; quantity: number }[]) {
  const transfer = await db.transferOrders.findUnique({ where: { id: transferOrderId }, include: { items: true } });

  await db.$transaction([
    // Decrease on_hand + reserved at source
    ...receivedItems.map(item => db.inventoryLevels.update({
      where: { variantId_locationId: { variantId: item.variantId, locationId: transfer.fromLocationId } },
      data: { onHand: { decrement: item.quantity }, reserved: { decrement: item.quantity } },
    })),
    // Increase on_hand at destination
    ...receivedItems.map(item => db.inventoryLevels.upsert({
      where: { variantId_locationId: { variantId: item.variantId, locationId: transfer.toLocationId } },
      create: { variantId: item.variantId, locationId: transfer.toLocationId, onHand: item.quantity, reserved: 0 },
      update: { onHand: { increment: item.quantity } },
    })),
    db.transferOrders.update({ where: { id: transferOrderId }, data: { status: 'received' } }),
  ]);
}

Step 3: Configure split-shipment communication

When an order is split across two locations, customers must be informed before confirming their order.

Shopify: Shopify's native checkout shows "Ships from multiple locations" in the shipping options when a split is needed. Customize the messaging in Settings → Checkout → Checkout language.

WooCommerce: Display a notice in the cart/checkout when ATUM detects a split is needed. ATUM Multi-Inventory includes configurable messaging for split shipments.

In the order confirmation email: Include all fulfillment groups with their expected shipping dates. "Your order will arrive in 2 shipments" with item breakdowns reduces support tickets.

Step 4: Balance stock across locations

Chronic stock imbalances (one warehouse overstocked, another out of stock) increase transfer costs and split fulfillments. Run a weekly analysis:

Signs of imbalance:

One location consistently has the same SKU at zero while another has excess
More than 20% of orders require split fulfillment for the same SKU
Transfer requests for the same product direction repeat every week

Action: Create a transfer order from the overstocked location to the understocked one before the next reorder cycle.

Shopify Stocky: Shows an "Inventory distribution" report that identifies imbalanced SKUs across locations.

Best Practices

Prefer single-location fulfillment — split shipments increase cost and confusion; exhaust single-location options before splitting
Use platform-native multi-location before buying an app — Shopify and BigCommerce handle the common case well; only add apps when routing logic is more complex than what the platform supports
Model transfer orders as in-transit inventory — reduce available stock at the source when the transfer ships; don't increment the destination until goods arrive and are counted
Inform customers of split shipments at checkout, not after purchase — finding out after payment feels deceptive
Run stock-balancing analysis weekly — a 15-minute review of the distribution report prevents chronic imbalances that compound over time

Common Pitfalls

Problem	Solution
Split fulfillment creates two shipping charges	Consolidate shipping cost at the order level; absorb the second shipment cost or notify the customer during checkout — never charge twice silently
Transfer received quantity differs from sent	Support partial receipt — record the actual received quantity per item and handle discrepancies (damaged in transit) separately
Inventory double-counted across locations	Each inventory record is location-scoped; when reporting total stock, always sum across locations explicitly
Location goes offline mid-fulfillment	Mark location as inactive; re-run allocation for unfulfilled orders assigned to that location
Customer confused about multiple tracking numbers	Send a separate tracking email per fulfillment with a clear note: "This is shipment 1 of 2 for your order"

Related Skills

@inventory-tracking
@low-stock-alerts
@catalog-import-export

multi-warehouse