Introduction

Managing inventory in a subscription-based business is fundamentally different from traditional eCommerce. While terms like product, variant, and SKU exist in both models, their meaning and impact vary significantly in a subscription context. This article explains how circuly handles stock management across different shop systems and provides guidance on how to set it up and automate it effectively.

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Feature Overview

circuly enables both manual and automated stock management, adapting to the setup of your shop system. The system updates stock when key order events occur: order placement, order cancellation, product return, and product swap.

Stock management behaviour depends on the shop system:

• Shopify / WooCommerce / Shopware: Variants can have the same SKU, and Circuly updates stock across all variants sharing that SKU.
• Saleor: Variants must have unique SKUs; Circuly uses automated N8N flows to harmonise stock between related variants.

circuly offers settings to automate stock updates for each event type.

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Step-by-Step Guide

Understanding key terms in subscription commerce

Before setting up stock, it's crucial to grasp these concepts:

• Product: In both eCommerce and subscription models, a product refers to a specific item available for sale. Each product has a unique name and description. A product is considered unique if it influences the available inventory.Example:
  If you offer iPhones on a subscription basis:
  • iPhone 14 Pro - 128 GB - Black is a different product from
  • iPhone 14 Pro - 512 GB - Black
  In traditional eCommerce, these would be considered variants of the same product. But in a subscription model, since they affect stock differently, they’re set up as separate products.
  

• Variant: Variants are different versions or options of a product that differ in certain attributes and affect customer choices. In subscription businesses, the contract duration is the most important attribute.Example:
  If you offer iPhone 14 Pro - 128 GB - Black with the following subscription durations:
  • Variant 1: 6 months (10 units)
  • Variant 2: 12 months (10 units)
  • Variant 3: 18 months (10 units)
  • Variant 4: 24 months (10 units)
  When a customer subscribes to the 6-month variant, stock for all variants must be reduced, because they all represent the same physical item.After the purchase:
  • Variant 1: 6 months → 9 units
  • Variant 2: 12 months → 9 units
  • Variant 3: 18 months → 9 units
  • Variant 4: 24 months → 9 units
  The underlying logic: one physical product, multiple durations = same inventory pool.
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• SKU (Stock Keeping Unit): A SKU is a unique identifier used to track inventory. In traditional eCommerce, each variant of a product (e.g., color, size) has its own SKU.In a subscription model, since variants are based on duration (not attributes like size or color), all variants often share the same SKU — especially in Shopify, WooCommerce, and Shopware.Important Distinction:
  • SKU helps categorize and group products.
  • But for actual stock tracking, every individual item should have a unique serial number.
  Example:
  If a customer orders the 6-month subscription for the iPhone 14 Pro - 128 GB - Black, and this product has 1 SKU, then all variants (12, 18, 24 months) should also decrease in quantity — because they're pulling from the same stock.Note for Saleor Users:
  Saleor does not allow multiple variants to share the same SKU. Therefore, extra configuration using N8N flows is required to synchronise stock across variants.

Shopify / WooCommerce / Shopware

Order Placement

• If "Check system stock" is enabled:
  circuly checks stock before checkout.
  Path: Settings > Checkout > PRE CHECKOUT > Check system stock

Scenarios:

  • ✅ Product is available: Checkout proceeds → Stock is reduced across all variants with the same SKU.
  • ❌ Product not available: Checkout is blocked.

Order Cancellation

• A webhook triggers a +1 stock update for all variants sharing the SKU.
• Setting Path: Settings > Orders > CANCELLATION > Restock items after an order cancellation

Return

• When a product is marked as returned in Circuly, a webhook adds 1 unit back to the stock for all variants with that SKU.
• Setting Path: Settings > Subscriptions > RETURN SUBSCRIPTION > Update stock on SKU level after return

Manual handling recommended if you differentiate between new and used stock.

Swap

• Swapping the same product triggers an automatic stock update (a new order is created).
• Swapping to a different product: select the new product from the dropdown to update stock automatically.

Saleor

Order Placement

• Since SKUs must be unique, Circuly uses N8N flows to sync stock across all durations.
• The flow ensures the correct physical stock is updated across duration-based variants.

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Order Cancellation

• A webhook is triggered and updates Saleor stock by +1.
• N8N harmonises the update across duration-based variants.

Return

• A return event triggers a webhook to update stock (+1) across all related variants.
• N8N ensures synchronisation.

Manual review recommended for distinguishing between new and used stock.

Swap

• Same product: stock updates automatically.
• Different product: select manually from the dropdown to trigger a new order and stock update.

Additional Settings

Here are the key settings to automate stock management:

EventSetting LocationCheck stock at checkoutSettings > Checkout > PRE CHECKOUT > Check system stockAuto-restock on cancelSettings > Orders > CANCELLATION > Restock items after an order cancellationUpdate on returnSettings > Subscriptions > RETURN SUBSCRIPTION > Update stock on SKU level after return

What Happens Next

Once your stock setup is configured in Circuly:

• Stock is automatically adjusted during key events: order placement, cancellation, return, and swap.
• For Shopify, WooCommerce, and Shopware, shared SKUs simplify the logic.
• For Saleor, Circuly’s N8N integration ensures accurate stock alignment across unique SKUs.
• For more efficient inventory tracking at scale, we recommend integrating a Warehouse Management System (WMS). Circuly triggers events, while the WMS handles real-time stock adjustments.

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