We usually2 supply barcode numbersin 13 digit EAN-13 format, with a leading 0(eg 0799439112766 ). However,these numbers can also be used in 12 digit UPC-A format without the leading 0 (eg 799439112766 ). The actual bars produced forboth of these are identical (see the picture below).
Outside of North America it is common toprint the barcode on products in the EAN-13 format. But keep in mind that some retailers have software systems that don’t like numbers with a leading 0, and hence they will prefer to use your barcode in the 12 digit format (eg 799439112766 ). This is still fine – the number is still the same and still unique and will work OK. You can let the retailer work out which version of your barcode number they will use.