Managing multiple SKUs for the same product: the fashion inventory challenge nobody talks about

Fashion retail has a problem that most inventory systems weren’t built to handle and it goes by many different names across the industry. 

“Linked lines”, “silent switches”, “Equivalent items“, “Double reference” or “supersession” refers to the retail phenomenon of when the same product (same fit, same commercial identity) lives under multiple SKUs at the same time, or across different seasons in a retailer’s system.

A white T-shirt that’s been in your range for three years. A large stock order split between two manufacturers. A popular carry-over style that comes back every season with a new reference. In each of these cases, your system sees several different products, but your business and customers see just one.

This disconnect creates real operational problems that are more common in fashion than most retailers realize.

Why does the same product end up with multiple SKUs?

There are two typical scenarios:

1. A large order split across suppliers

You need a high volume of a core product (e.g. white socks) and no single manufacturer can fulfill the whole order, so you split it between two suppliers. The product is identical, but it enters your system under two different SKU codes which are both now selling concurrently across your stores and online channels.

How do you track inventory across both? How does a replenishment order for SKU A account for the stock available under SKU B? If your system doesn’t link them, you can’t.

2. A continuity product returning season after season

Your red dress sold out last season, and you’re bringing it back: same style, slightly different fabric or a new manufacturer. It’s a new season and it’s a new SKU, but from a demand forecasting perspective, it’s the same product with a rich sales history. If your system treats it as brand new, that history disappears and your forecast starts from zero.

This is the core of what the industry sometimes calls supersession (when one product reference replaces or succeeds another) and it’s a challenge that generic inventory systems handle poorly or not at all.

What happens when your system can’t connect equivalent SKUs?

The consequences compound quickly:

• Fragmented demand history leads to unreliable forecasts, especially for returning or carry-over references
• Split stock signals mean the system can’t see the full picture of what’s available in the warehouse
• Replenishment imbalances: stock of one reference sits idle in the warehouse while another runs out in stores, even though they’re the same product
• SKU proliferation gets worse over time, adding noise and complexity to every report and decision

The typical fix is manual workarounds, merchandisers connecting the dots themselves, adjusting forecasts by hand, chasing warehouse teams to reallocate stock. It works, but it doesn’t scale.

How Nextail handles equivalent SKUs: linked lines

At Nextail, we call this capability linked lines. The idea is straightforward: group all equivalent product references into a single chain, ordered by logistical consumption priority (a “lineage”), and anchor all inventory calculations to one active reference.

Here’s how it works:

1. All data is aggregated under a single reference

Sales history, stock levels, stockouts, and cover from every reference in the chain are unified. If a product sold 200 units under last season’s SKU and 150 under this season’s, Nextail sees 350, not two separate products with 200 and 150.

2. All calculations run on that single line

Forecast, replenishment needs, business rules, and parameters are applied once, on a complete picture of the product. No fragmentation, no duplication.

3. Replenishment is disaggregated by logistical consumption priority

Nextail determines which reference to pull from the warehouse first and generates replenishment orders using the original SKU codes. Stores and warehouses continue working with the references they know, without any operational disruption.

4. Size curves and pack differences are factored in 

Equivalent SKUs don’t always come in the same sizes or the same minimum logistic units (packs) especially when split across manufacturers. These constraints are factored into every replenishment decision, so the system sends what’s actually available and operationally feasible, not just what’s theoretically optimal. 

Who benefits most from this?

Linked lines have the highest impact for retailers with a significant share of basics, continuity products, or carry-over styles: lingerie, hosiery, footwear basics, core sportswear, kidswear essentials. These are often the most predictable lines in your range, but only if your inventory system can see them whole.

When it can, your merchandising team gets forecasts built on the full history of a product, not a fragment of it. Replenishment runs automatically on a complete view of warehouse stock. And the manual work of connecting equivalent references disappears.

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Contact us for more information on how Nextail can help you automate and streamline your inventory management!