How inventory software uses SKUs and barcodes

Software treats a scanned code as text. It looks that text up in its list of items and finds the one record that matches. That's the whole trick. Everything else is what the software does after the match.

What a scan actually sends

• Just characters. A barcode scanner reads the pattern and sends the data it contains to a computer.¹
• As if typed. A keyboard wedge type of scanner sends characters that appear exactly as if they had been typed at the keyboard.¹
• So typing works too. If a label is damaged, a person can type the same code into the same field.

What the software does next

• Matches the code to an item. Zoho Inventory's help page says you have to key in the bar code of the item as the SKU of the item, either manually or with a scanner. After that, a scan can find the item. Checked 7 November 2026.²
• Adds it to the transaction. In Zoho Inventory you place the cursor on the Item Details field of a new invoice or bill, then scan, and the line item is added. Each further scan adds another.²
• Counts per unit. Stock levels are kept per SKU, as the quantity of each unit.³
• Tracks serial numbers. Zoho says scanning can also be used on serial numbers, when serial number tracking is enabled for the item.²

This describes one maker's documented steps. Other products use different screens and settings, so follow the help pages for the one you use.

Which field holds the code?

• The SKU field. In the Zoho example above, the scanned code is the SKU.²
• A separate barcode or GTIN field. Some products keep these apart from the SKU. Look in the item settings.
• Both. If your software lets you store several codes against one item, you can keep your own SKU and the maker's GTIN together.

A GTIN identifies a trade item in a database, and it can be used to look up product information.⁴ Your SKU does the same job inside your own records. How SKUs and GTINs differ covers the details.

Setting up so scans work

• Enter the code on the item first. The record has to hold the code before a scan can find it.²
• Keep one item type to one code. A GTIN belongs to one kind of trade item, so two products shouldn't share one.⁴
• Match the length and characters. A code on the label has to be exactly the code in the record. No missing zeros, no extra spaces.
• Test with a few items. Scan one in each group before you relabel everything.
• Read the maker's help page. Features and plans change, so note the date you checked.

If a scan finds nothing

• Compare the two codes. Scan into a plain text box and read what appears. Then open the item record and read the stored code.
• Look for hidden characters. Spaces or line breaks sometimes come along with a pasted code.
• Check the symbol type. The scanner may not be set to read it. See barcode scanner types.
• Check the print. A faint or cramped label can read wrongly. See printing barcode labels.

What software doesn't do

• It doesn't make a SKU valid. You decide the pattern, as the numbering checklist explains.
• It doesn't issue product barcode numbers. GS1 hands out the digits behind UPC and EAN codes.⁵ Read where they come from for the route.
• It doesn't fix a mislabelled shelf. A scan only confirms that the code matches a record.