Why I Use SKUs and Why I Think Sellers Should Start Early
BEHIND THE SHOP
How a simple inventory number keeps cards, comics, photos, listings, and orders connected at Next Level Collectibles.
Back when I was in the Marines, I worked in supply administration. Everything we managed, from everyday supplies to specialized gear, had an identifying number. Those codes were not random. They told us exactly what we were handling and helped keep inventory organized.
Later, while working at Home Depot, I saw the same idea in a different setting. Every product, whether it was carpet, hardware, or tools, had a SKU connected to its identity, pricing, and inventory.
So when I started selling cards and comics, I knew I wanted a system from the beginning.
That system is the SKU.
What a SKU does for my inventory
A SKU is simply a unique internal ID assigned to one specific item. It is not something buyers see in my listings. It is a tool that helps me make sure the item in front of me is the exact item connected to the right photos, listing, order, and buyer.
My first format was TCB-0001, with TCB meaning Trading Card Basketball. Basketball was the biggest part of my card inventory and the sport I knew best, so it made sense as my starting point.
As I brought in more sports, I continued using that sequence for cards. Going forward, comics will have their own separate format beginning with COM-0001. The important part is not that the code describes every detail about the item. The important part is that each SKU is permanent and unique.
Once a number is assigned, it is never assigned again.
My SKU system is built to grow with the business
Right now, the SKU itself does not tell me the player, sport, year, condition, or storage box. Those details live in my database, where they can be updated as my inventory changes.
That database can hold the information that actually matters for each item:
Player, character, or title
Year, set, issue number, and card number
Parallel, team, condition, and price
Storage location and inventory status
Front and back image links
eBay, Squarespace, and Whatnot listing status
This gives every card or comic one permanent identity, while the other information stays flexible.
For example, I may eventually expand to enough inventory that I need separate boxes by conference, sport, or collection. Instead of changing a SKU, I can simply update the storage location in the database.
How SKUs connect my scan to listing workflow
For cards, I assign the SKU after scanning. The scans first go into an inbox folder on my computer. From there, my workflow assigns a brand new unused SKU, uploads the images to my host, and renames the files around that SKU.
A Kobe Bryant card, for example, might become:
TCB_1851_front
TCB_1851_back
That means the images are permanently tied to the same card record from the beginning.
I also use a small amount of AI in the workflow to help analyze the scanned card and organize the item information. It still needs my review, especially for details like sets and parallels, but the SKU keeps the scans, analysis, and database record connected as the item moves toward a listing.
That is a huge improvement over trying to remember which front and back image belongs to which card after scanning a large batch.
It helps prevent duplicate work and listing mistakes
The SKU is also what will make cross listing much more manageable as my system grows.
If one card is listed on eBay and Squarespace, I do not want to search both sites manually by player name, set, or photo just to confirm it is the same card. With one SKU in the database, I can see where that exact item is listed.
If TCB-8563 sells on Squarespace, I can search that SKU on eBay and remove the matching listing. For now, that part is still manual, but the database is being built with the goal of eventually syncing inventory and flagging mismatches between platforms.
That means the system can alert me when an item is listed somewhere it should not be, instead of relying on memory and hoping I catch it in time.
SKUs have already saved me from shipping the wrong item
This is not just about future automation. It has already helped me in a very real way.
I once sold two cards of the same player that were different cards going to different buyers. Luckily, the SKU was printed on the eBay invoice. When I checked the invoice against the card, I noticed that I had the wrong one.
That last SKU check kept me from shipping the wrong cards to two different buyers.
When I pull an order, I usually start with the team, then the player, and finally confirm the exact SKU. My cards are organized by team in divided storage boxes, so that process gets me close quickly. The SKU makes sure I pull the exact copy the buyer purchased, especially when I have multiple versions of the same player or even multiple copies of the same card.
A simple system is enough to start
I would tell a seller with 50 cards or 20 comics not to think of SKUs as overkill. It is a small step that becomes much harder to build into your process later.
You do not need a warehouse, expensive software, or a complicated code to start. You can begin with something as simple as:
CARD-0001
COM-0001
Put the label on a top loader, sleeve, team bag, or comic bag. Never put a sticker directly on the card or comic itself.
Then keep a basic spreadsheet or database with the SKU, item name, price, status, and location. As your inventory grows, that one small habit can save you time, reduce mistakes, and give you a foundation for better listing and inventory tools.
Get the infrastructure right early. Your future self will be glad you did.
Follow Next Level Collectibles Behind the Shop for more collector focused guides, inventory tips, and a look at how we build better systems for comics and cards.
