How to build a SKU numbering system

There's no official format, so the work is deciding a pattern and sticking to it. These identifiers are not regulated or standardised.¹

Before you pick a pattern

• Decide what makes two items different. A SKU stands for an item type and all the attributes that distinguish it from other item types.¹ Write those attributes down first. Size? Colour? Pack quantity?
• Decide whose code you'll use. You may keep your supplier's code, or invent your own.¹ Your own codes stay stable if you change supplier.
• Check your software's rules. Look for length limits, allowed characters and whether the SKU field is also used for scanning. Check whether your software has a separate barcode or GTIN field. Zoho's help page, for example, has you enter the barcode as the SKU. Checked 7 November 2026.²

Rules that keep codes clear

• Use a fixed pattern. Every code should read the same way, from left to right: group, item, option.
• Keep it short. Short codes are quicker to type, and easier to read out over the phone.
• Use capital letters and plain characters. Skip spaces, slashes and accents.
• Pad numbers with leading zeros. Lists then sort the way you expect, because every number has the same length.
• Avoid look-alikes. The letter O and the digit zero get mixed up. So do the letter I, the letter L and the digit one.
• Keep one item type to one code. No two items share a SKU, and no item has two.

A pattern that grows

• Group. Two or three letters for the family, such as MUG for mugs.
• Item. A running number inside the group. It's recommended that companies hand out GTIN item numbers one after another, such as 001, 002, 003.³ The same idea works for SKUs.
• Option. A short suffix for size or colour, such as BLU for blue.

An example in this pattern is the group MUG, then the running number for the item, then BLU. A person can read the family and the colour at a glance, and the middle part stays unique.

What not to build into a code

• Don't pack in facts that change. A price, a supplier name or a shelf position will be out of date one day. The code will not change, so it ends up wrong.
• Don't reuse a retired code. Old orders and counts still point to it. A new item given the old code inherits that history.
• Check before reusing a GTIN as your SKU. Some software, such as Zoho Inventory, has you enter the barcode as the SKU (checked 7 November 2026), so check how yours handles a GTIN.² Each different type of trade item is allocated a different GTIN.³

Test before you commit

• Take a couple of dozen real items and code them on paper.
• Ask a colleague to read three codes aloud and spell them back.
• Import the sample into your software and scan or type each code.
• Look for ties, where two items could take the same code. Fix the rule, not just the item.

Once the pattern works, write it on one page and keep it where staff can see it. Then printing barcode labels and the scanner types are the next practical steps.