How to create an eBay SKU system that scales

Where SKUs go on eBay

eBay calls the SKU the Custom label (SKU). You can add it when you create or revise a listing, it holds up to 50 characters, and you can use it to find listings in Seller Hub. Many inventory, listing and shipping tools match items to eBay listings by this field, so it is worth keeping clean.

What makes a good SKU

• Unique. One SKU points to one item or one listing, never two.
• Short. Shorter codes mean fewer typos and fit on small labels. Fifty characters is a limit, not a goal.
• Plain characters. Stick to capital letters and numbers inside the code itself.
• No leading zeros. Spreadsheets often strip them, which silently turns 00042 into 42.
• Never reused. Once a SKU has belonged to a product, do not give it to a different one.
• Stable meaning. Every part of the code should mean the same thing on every label.

Three common SKU formats

There is no single right answer. If speed of picking matters most, a location-based SKU is hard to beat. If items move around a lot, a sequential SKU with a separately recorded location is easier to keep accurate.

Location-based SKUs in practice

This is the format Scanmerce’s label tools are built around:

• 212 is the shelving unit number.
• A is the level on that unit.
• 1 is the item number on that shelf.

Because every shelf has its own sequence, you can print a roll of labels for a shelf in advance, 212A1 through 212A100, and stick the next one on each item as it is shelved. As long as each range is printed only once, every label carries a number that has never been used, which prevents most duplicate SKUs before they happen.

The weak spot is movement. If 212A1 moves to shelf 305B, either relabel it or record the move so the system knows where it really is. Whichever rule you choose, apply it every time.

Adding lister initials for accountability

Teams often want to know who listed each item. One clean way is to add the lister’s initials after a space: 212A1 TM. The part before the space stays the scannable SKU, and the initials show who created the listing. Scanmerce’s labels and barcodes use only the part before the space, so the package label still reads 212A1.

How duplicate SKUs happen, and how to prevent them

Duplicate SKUs cause wrong picks, incorrect stock counts and confused tools. They usually come from:

• Copying an old listing and forgetting to change the custom label.
• Two people working from the same number sequence.
• Typos, especially between similar characters such as 1 and I or 0 and O.
• Relisting an item under a new SKU while the old listing is still active.

Prevent them with one source for the next number, such as pre-printed label rolls per shelf, and review duplicates regularly. Scanmerce keeps unresolved duplicate SKUs visible in a shared alert queue, and its Sell Similar option starts a new draft without copying the old SKU.

Printing SKU labels

Code 128 barcodes encode letters and numbers compactly, which makes them a good fit for SKUs. Print at actual size (100% scale) with the paper size set to match your label roll, and print a single test label before a big batch. A 2 × 1 inch label is plenty for a short SKU.

Rolling out a new SKU system

1. Write the format down in one sentence everyone can follow.
2. Use it for all new inventory starting today.
3. Convert existing stock one shelf at a time, starting with your fastest sellers.
4. Update the eBay custom label whenever you revise an older listing.

Pair the new SKUs with a shelf system from our guide on organizing eBay inventory, and see how Scanmerce uses them for inventory locations and alerts.