What is SKU?

What is a Stock Keeping Unit, and how is it different from an ASIN?

A stock keeping unit is an internal code a seller uses to identify and count a specific product. You decide what it looks like. Amazon never shows your SKU to shoppers; it's purely for your operations. The ASIN, by contrast, is Amazon's public product ID shared by every seller of that product. The same ASIN can be sold under thousands of different sellers' SKUs.

This split is why a clean SKU scheme pays off. Because you define the SKU, you can encode useful information into it: brand, product line, variation, supplier, or batch. A common pattern is something readable like BRAND-PRODUCT-SIZE-COLOR. The goal is a code that is unique, stable, and human-legible, so that when a SKU shows up in a settlement report or a reimbursement case, you instantly know which product and which cost it refers to.

• •You assign and control the SKU; Amazon assigns the ASIN
• •The SKU is private to your account and never shown to shoppers
• •One ASIN can be sold under many sellers' SKUs
• •Good SKUs are unique, stable, and human-readable
• •Encode brand, variation, and supplier to speed reconciliation

How to find a SKU number on Amazon

To do an Amazon SKU lookup, go to Seller Central and open Manage Inventory; the SKU column sits next to each listing alongside its ASIN and FNSKU. You can also search inventory by SKU directly, export the full list to a flat file, or pull SKUs through the Amazon API. Your settlement reports and FBA inventory reports are likewise keyed by SKU, which is what makes the SKU the natural join key when you reconcile payouts to products.

One place the SKU shows up physically is on your FBA units. When you create a shipment, Amazon generates the barcode labels from your SKU (the FNSKU is derived from it), and those Amazon SKU labels are what the fulfillment center scans on receipt. Print them from the shipping workflow rather than reusing an old PDF, because a label carried over from a previous SKU sends units into the wrong pool and turns into a research case weeks later.

If you sell across channels, note that platforms use the term the same way: a Shopify stock keeping unit, an Etsy SKU, and an Amazon SKU all serve the same role on their respective storefronts. Sellers running multichannel operations usually maintain a master SKU and map each marketplace's SKU back to it, so that a single product's cost and inventory aren't fragmented across systems. Keeping those mappings tight is what prevents overselling and double-counted inventory.

How to design a SKU scheme that survives scale

The best time to design a SKU scheme is before your tenth listing. The second best time is now, because retrofitting one at 500 SKUs is genuinely painful. Start with a fixed pattern and never deviate: a brand or line prefix, a product code, then variation attributes, each segment separated by hyphens. Something like KTC-BOTTLE-32-BLU reads instantly as "Kitchen line, bottle, 32oz, blue." Keep it under about 20 characters, use only capital letters, numbers, and hyphens, and never use spaces or characters that break CSV exports.

Two decisions matter more than the rest. First, decide whether batches get their own SKUs. If your unit cost changes meaningfully between purchase orders, a batch suffix (like -B2 or a date code) keeps each cost layer cleanly separated, at the price of more SKUs to manage. Sellers whose costs are stable usually skip this and let their inventory software track cost layers under one SKU instead. Either choice works. Mixing the two choices randomly doesn't.

Second, never reuse a retired SKU for a different product. Amazon keeps historical data attached to the SKU, and so does your accounting system. Resurrect an old code for a new item and you've welded two products' sales history, returns, and costs together permanently. Also resist the temptation to accept Amazon's auto-generated SKUs (those long random strings). They're unique, but they carry zero information, and every reconciliation task from then on requires a lookup table just to know what you're looking at.

A worked example: one product, three channels, one master SKU

Say you make soy candles and sell one scent in two sizes on Amazon, Shopify, and Etsy. That's two physical products but potentially six channel listings. The clean setup: master SKUs CANDLE-LAV-8 and CANDLE-LAV-12 in your inventory system, with each channel's listing SKU either identical to the master or mapped to it. You hold 400 units of the 8oz at a $4.20 landed cost and 250 of the 12oz at $5.90. All hypothetical numbers, but this is the exact shape of a real multichannel catalog.

Now the week's sales come in: 60 units of the 8oz on Amazon, 25 on Shopify, 10 on Etsy. Because every channel resolves to the same master SKU, your inventory system decrements one pool (400 down to 305) and your COGS for the week is simply 95 times $4.20. No channel is guessing at its own stock level, and no product exists twice in your books. This is the whole argument for master SKUs in one paragraph.

Now break it, the way sellers actually break it. Suppose Etsy listings were created with a different code, say LAVCANDLE8, and never mapped. Your inventory system doesn't recognize the sales, so the pool shows 315 units when only 305 exist. Eventually Amazon or Shopify sells candles you don't have, and you're canceling orders (an oversell) or scrambling to make stock. Meanwhile the 10 Etsy units either never hit COGS or get booked as some catch-all adjustment. Multiply this by 50 products and two years, and you've described why so many sellers' books can't survive due diligence.

Why your SKU scheme drives clean COGS and inventory value

Cost of goods sold and inventory valuation are calculated per SKU. When you receive stock, the landed cost attaches to the SKU; when a unit sells, that SKU's cost flows into COGS. If two different products share a SKU, or if you reuse an old SKU for a new product with a different cost, your cost layers blend and your margins become unreliable. A disciplined one-product-one-SKU rule keeps valuation honest.

The same logic powers reimbursement accuracy. Amazon reports lost and damaged units by SKU and FNSKU, so the SKU is how you connect a warehouse loss back to the actual unit cost you paid. BeanHawk uses the SKU as the anchor to match settlement lines, inventory movements, and recovered reimbursements to the right product, so your books reflect true per-product profit rather than a marketplace-level blur.

The bookkeeping treatment: where SKUs live in your accounting stack

SKUs belong in your subledger, not your general ledger. The ledger (QuickBooks, Xero) should carry summarized entries: a settlement journal for revenue, fees, and refunds, plus periodic COGS and inventory-value postings. The per-SKU detail (quantities, cost layers, per-product margin) lives underneath in your inventory or accounting tool. Sellers who create a QuickBooks item for every SKU learn the hard way that a 300-SKU item list with marketplace fees sprinkled across it is unmaintainable, and their accountant learns it at billable rates.

Tooling follows the same split. Ecommerce inventory management software owns the SKU layer: stock levels per channel, cost layers, reorder points, and the master-SKU mapping that keeps Amazon, Shopify, and Etsy pointing at one pool of stock. If you're on multiple channels, multi channel inventory management software with real SKU mapping is the difference between one source of truth and three arguing spreadsheets. Then amazon accounting software (or its Shopify and eBay equivalents) translates settlement data into ledger journals keyed by those same SKUs, which is what makes per-product profit reports possible at all.

If your ledger is QuickBooks, the practical question when evaluating quickbooks for amazon sellers or shopify accounting software isn't "does it connect", it's "what happens to my SKUs on the way through." Good connectors (A2X, Link My Books, BeanHawk among them) summarize the ledger entry but preserve SKU-level detail for costing and analysis. Weak ones flatten everything into one revenue line, which balances fine and tells you nothing. And to be fair to spreadsheets: under a couple dozen SKUs on a single channel, a well-kept sheet with one row per SKU is a perfectly respectable subledger. The tools earn their fee when channels multiply and the mapping work stops being a Sunday chore.

Common SKU mistakes

SKU problems compound quietly. Each of these looks harmless on the day it happens, and each one costs real reconciliation hours (or real money) months later.

• •Accepting Amazon's auto-generated SKUs, leaving you with meaningless random strings across every report
• •Reusing a retired SKU for a new product, permanently welding two products' history and costs together
• •Running different, unmapped SKUs for the same product across channels, which double-counts inventory and invites oversells
• •Encoding data that changes (like price) into the SKU, forcing renames that break historical continuity
• •Using spaces or special characters that corrupt CSV exports and API calls
• •Blending unit costs across batches under one SKU without software that tracks cost layers, making COGS a guess
• •Deleting a SKU in Seller Central to "clean up", then losing the join key for old settlement lines and reimbursement claims

Frequently asked questions

What is a SKU number on Amazon?

A SKU (Stock Keeping Unit) number on Amazon is the seller-defined identifier you assign to each product you list. It is private to your account, used to track inventory and costs, and distinct from the ASIN, which is Amazon's public product ID.

How do I find my SKU number on Amazon?

Open Seller Central, go to Manage Inventory, and the SKU appears next to each listing alongside the ASIN and FNSKU. You can also search by SKU, export the inventory file, or retrieve SKUs through the Amazon API and your settlement reports.

What does SKU mean on Etsy or Shopify?

The SKU meaning on Etsy and Shopify is the same as anywhere else: a Stock Keeping Unit is the seller's own identifier for a product or variation. Both platforms put a SKU field on the listing form and leave it optional, which is where the confusion starts, because a blank field costs nothing on day one and costs you a stock pool later. The listing SKU meaning is simply "which of my products is this offer", so fill it with your master code on every variation. That's what lets multichannel sellers map an Etsy SKU and a Shopify stock keeping unit back to one Amazon SKU and one pile of physical stock.

What makes a good SKU scheme?

A good SKU is unique, stable, and human-readable, typically encoding brand, product line, and variation in a consistent pattern. Avoid reusing retired SKUs for new products, because shared SKUs blend cost layers and corrupt your COGS and inventory value.

What is the difference between a SKU and an FNSKU?

A SKU is the identifier you assign to an offer in your own records. An FNSKU is the barcode Amazon generates from that SKU and prints on the physical unit so its warehouses can track your inventory. One SKU produces one FNSKU per condition when enrolled in FBA.

Can I change a SKU on Amazon after creating it?

No, not on the existing offer. Amazon SKUs are permanent once created; the only route is to close the listing and recreate the offer under a new SKU, which splits your sales history across two codes. That's why it pays to get the naming pattern right before you list, not after.

Does QuickBooks track inventory by SKU for marketplace sellers?

QuickBooks can track items, but it wasn't built for marketplace SKU volume, multi-channel stock pools, or per-batch cost layers. The pattern that holds up is keeping SKU detail in ecommerce inventory management software or a connector's subledger, and posting summarized journals to QuickBooks. Trying to mirror hundreds of marketplace SKUs as QuickBooks items usually collapses under fee allocation and sync errors.

What software should I use to manage SKUs across Amazon, Shopify, and Etsy?

You need two capabilities, sometimes in one tool: multi channel inventory management software that maps every channel listing to a master SKU and one stock pool, and accounting software that carries SKU-level COGS into your ledger. Compare tools on how they handle SKU mapping, cost layers, and settlement summarization; BeanHawk, A2X, and Link My Books all approach the accounting side differently, and a small single-channel catalog may not need more than a spreadsheet yet.

Related terms

Go deeper

• COGS for Amazon Sellers: Getting Cost of Goods Sold Right
• Ecommerce Inventory Management: Quantity, Value, Reorder Points