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A stock-keeping unit or SKU is a number or code used to identify each unique product or item for sale in a store or other business.

It is a unique identifier

Unique identifier

With reference to a given set of objects, a unique identifier is any identifier which is guaranteed to be unique among all identifiers used for those objects and for a specific purpose...

 for each distinct product and service that can be purchased. The usage of SKU is rooted in data management

Data management

Data management comprises all the disciplines related to managing data as a valuable resource.- Overview :The official definition provided by DAMA International, the professional organization for those in the data management profession, is: "Data Resource Management is the development and execution...

, enabling the company to systematically track its inventory or product availability, such as in warehouses and retail outlets. They are often assigned and serialized at the merchant level. Each SKU is attached to an item, variant, product line

Product lining

Product lining is the marketing strategy of offering for sale several related products. Unlike product bundling, where several products are combined into one, lining involves offering several related products individually. A line can comprise related products of various sizes, types, colors,...

, bundle, service, fee, or attachment. SKUs are often used to refer to different versions of the same product. For example, a retail store carrying the game Guitar Hero 3 might have six SKUs, two for each of the three platforms

History of video game consoles (seventh generation)

In the history of video games, the seventh generation of consoles is the current generation , and includes consoles released since late by Nintendo, Microsoft, and Sony...

—one with and one without a guitar controller.

SKUs are not always associated with actual physical items, but are more appropriately billable entities. Extended warranties

Warranty

In business and legal transactions, a warranty is an assurance by one party to the other party that specific facts or conditions are true or will happen; the other party is permitted to rely on that assurance and seek some type of remedy if it is not true or followed.In real estate transactions, a...

, delivery fees, and installation fees are not physical, but have SKUs because they are billable. All merchants using the SKU method will have their own approach to assigning the SKU system based on regional or national corporate data storage and retrieval strategies. SKU tracking varies from other product tracking methods which are controlled by a wider body of regulations stemming from manufacturers or possibly third-party regulations.

Successful inventory management systems assign a unique SKU for each product and also for its variants, such as different versions or models of product or different bundled packages including a number of related products. This allows merchants to track, for instance, whether blue shirts are selling better than green shirts. Other entity tracking methods, with varying regulations, are Universal Product Code

Universal Product Code

The Universal Product Code is a barcode symbology , that is widely used in North America, and in countries including the UK, Australia, and New Zealand for tracking trade items in stores. Its most common form, the UPC-A, consists of 12 numerical digits, which are uniquely assigned to each trade item...

 (UPC), European Article Number

European Article Number

An EAN-13 barcode is a 13 digit barcoding standard which is a superset of the original 12-digit Universal Product Code system developed in the United States...

 (EAN), Global Trade Item Number

Global Trade Item Number

Global Trade Item Number is an identifier for trade items developed by GS1...

 (GTIN) and Australian Product Number (APN).

Example SKU systems

Good data design practice demands that identifiers be meaningless. This provides maximum flexibility, because a code with a meaning can easily overflow the number of characters allotted, conflict with that of a new characteristic, etc. While a meaningless SKU will be more difficult for humans to relate a product, automated systems can do so without any limitation. The following are 7 common SKU systems:

Example 1:

An imaginary product, called a widget

Widget (economics)

The word widget is a placeholder name for an object or, more specifically, a mechanical or other manufactured device. It is an abstract unit of production. The Oxford English Dictionary defines it as "An indefinite name for a gadget or mechanical contrivance, esp. a small manufactured item" and...

, has a part number

Part number

A part number is an identifier of a particular part design used in a particular industry. Its purpose is to simplify referencing to that part...

 of 1234. It is packed 20 to a box, and the box is marked with the same part number 1234. The box is then placed in the warehouse. The box of widgets is the stock keeping unit (SKU), because it is the stocked item. Even though the part numbers are interchangeable to mean either a widget or a box of widgets, the box of widgets is the stocked unit. There may be three different colors of widgets; each of these colors will be a separate SKU. When the product is shipped, there may be 50 boxes of the blue widgets, 100 boxes of the red widgets, and 70 boxes of the yellow widgets shipped. That would be a shipment of 220 boxes, across three SKUs that may be designated 1234B, 1234R, and 1234Y.

Example 2:

A product is given an article number 4321. Within the last 2 years Vendor X has been making article number 4321. Vendor X is going out of business, yet the plans for making article 4321 still belong to the selling company. The selling company now has two companies making the same product during the transition phase. Instead of tracking variants by maker, it uses UPCs (Universal Product Code

Universal Product Code

The Universal Product Code is a barcode symbology , that is widely used in North America, and in countries including the UK, Australia, and New Zealand for tracking trade items in stores. Its most common form, the UPC-A, consists of 12 numerical digits, which are uniquely assigned to each trade item...

), and possibly "color" or "dye" or similar. It will still hold the same article number for daily, weekly, monthly, quarterly, and yearly profit margins. SKUs link UPCs from the vendor to the retail company. A single UPC can have many SKUs. Makers use UPCs to see if it is worth making green when red products account for 99% of the market. Selling companies use SKUs to see which company performs better with the same item.

Example 3:

If a particular product has a MRP (Maximum Retail Price) of x and there is a revision in price, say the price now becomes y, then x and y will have to be stocked separately and billed separately so they become two different SKUs. SKUs can then be printed into a barcode and placed on the product. When scanning SKUs, the system recognizes the price and prepares the sale for that price.

Example 4:

A SKU may contain all the common properties of an individual item. So, for instance, an SKU for a pair of Levi's 36" green straight-leg jeans might be LEV-JN-SL-36-GN or LEVJNSL36GN, where LEV stands for the vendor Levi's, JN means Jeans, SL means Straight Leg, 36 stands for 36" waist, and GN stands for Green. Typical abbreviations are 2-4 characters long, and it's a good idea to make sure all abbreviations for one property are the same number of characters (so for instance, use RD and BU for Red and Blue, rather than RED and BLUE). This way all your SKUs are the same number of characters, and makes it easy to de-code a SKU without looking it up. If a size may be two or three dimensions, like 2x4, 4x6x8, or 2'4"x5'6", you may wish to create a numbering system for the sizes. If for example a size is 8X10, and you want all size abbreviations 3 characters, you could turn the 10 into a letter like A, so it reads 8XA. The number 11 would then be B, 12 is C, and so on. This methodology is used by companies who sell high-ticket items which have many variations in features.

In the following table, vendors, collections, designs and colors are each numbered 1-6; the product highlighted has the SKU V4C3D5C2.

Vendor 1	Collection 1	Design 1	Color 1
Vendor 2	Collection 2	Design 2
Vendor 3		Design 3	Color 3
	Collection 4	Design 4	Color 4
Vendor 5	Collection 5		Color 5
Vendor 6	Collection 6	Design 6	Color 6
→ SKU = V4 + C3 + D5 + C2 (V4C3D5C2)

Example 5:

Another example: an item may be a can of a certain soft drink

Soft drink

A soft drink is a non-alcoholic beverage that typically contains water , a sweetener, and a flavoring agent...

with an item identifier number of 1234. If that item is held in stock in the warehouse and two retail stores, it is said that there are three items and one SKU to be maintained. An item in two different bin locations in the same geographical location is not seen as two SKUs as they are managed as a single unit.

Example 6:

Some products remain the same but get updated each year or season. With such items - typically apparel - it can be helpful to have the date as part of the code for the SKU. For instance, an extra large white T-shirt could be given a SKU of the form 12345-09-WHT-XL. The version for the 2010 season could have a different print on it, thereby being a different product and needing a new code, e.g. 12345-10-WHT-XL.

It may not always be desirable to have the year code easily identifiable in the SKU. For instance, 12345-05-WHT-XL could be the SKU for an extra large white T-shirt that dates from the 2005 model year. This detail in the stock code could be picked up on by the retailer with the result that the 2005 version of the T-shirt stays in the wholesaler's warehouse for even more time. If the 2005 T-shirt had a more innocuous code, e.g. 7A12345-WHT-XL, then the model year can only be deciphered by those that know that codes beginning with '7A' date from 2005.

Even if the product does not change from year to year the stock may still need to be rotated. Having the year embedded in the SKU code can help, however, the whole retail chain involved in the wholesaling, distribution and retail of the product will need to spend time updating codes every year/season. This is an administrative overload that could delay the roll-out of the product.

Example 7:

Some products are commonly sold both individually and in full-case quantities. These items receive two SKUs: a "parent" SKU for the full case and a "child" SKU for the individual item. For instance, a case of glue might have SKU 1234 while a bottle of glue might have SKU 2345. To encourage people who use a lot of glue to purchase full cases of it, they often sell at a discount. Both the case and the individual bottles will be marked with separate UPCs. The store's inventory control system is designed to work with the parent and child UPCs. If there are 12 bottles in a case, a store that has 65 bottles of glue in stock will count them as five SKU 1234 and five SKU 2345 for inventory purposes. As single bottles are sold, it will decrement the single-unit SKU until that SKU reaches zero units. It will then deduct one full case from the parent SKU inventory and add the number of bottles it contained to the single-unit inventory because a store employee will replenish the empty shelf by taking glue out of a full case.

A limited number of products are sold in "master pack" quantities in addition to single-piece and full-case lots. Floor tile is an example. A particular style of tile with SKU 3456 may cover one square foot of floor space and come in a case of 12 tiles which has SKU 4567. As one box of tile is far from being enough to install a floor, manufacturers package 15 boxes of tile on a pallet and sell the pallet as a master pack, which has SKU 5678.
Systems using parent/child/master pack SKU systems are designed so employees may only order even multiples of the largest pack size. An employee may order 15 of SKU 4567, one of SKU 5678 or 180 of SKU 3456; if the employee orders 100 of SKU 3456 the system will reject the order and ask the employee to resubmit the request in a multiple of 180. As the system is programmed with the number of SKU 3456 and the number of SKU 4567 that are in SKU 5678, the system will automatically translate an order for SKU 3456 or SKU 4567 into an order for the correct number of SKU 5678.—————≤≤