Usually, we supply barcode numbers of 13 digit EAN-13, with a format of leading 0 (eg 0799439112766 ). However, these barcodes numbers can also be used in 12 digit UPC-A format but without the leading 0 (eg 799439112766 ). The actual bars produced in the barcode numbers for both of these are the same (see the picture below).
Outside of North America, it is common to print the barcode on products in the EAN-13 formation. However, some retailers have software systems that don’t recognize the numbers with a leading 0, and hence they will prefer to use your barcode in the 12 digit format (eg 799439112766). Which is fine – the number is still the same and still unique and will work OK. You can let the retailer figure out which version of your barcode number they will use.