For details about symbol size requirements, see Guidelines for Supply Chain Identification , Section 4.18. The height of the bar code symbol is important to its scannability. When a bar code is shorter than specified in the UCC Quality Specification for the U.P.C. Printed Symbol manual, retailers have problems with scanning at the checkout. Truncation, or shortening of the bar code symbol, is strongly discouraged. Avoid truncation to ensure good scannability of coupons.
Color is also important.
The best colors for a bar code symbol are black for the bars and white for the spaces. These colors are the easiest colors for a scanner to read. For the bars, avoid any colors with red or reddish tints, such as certain browns, purples, and oranges, and light colors, such as yellow or pastel colors. For the spaces, avoid dark colors. If the encodation is incorrect, the scan will not match with the correct family of products on the retailer's file, the Value Code could be incorrect, the wrong product could be validated, or it will not scan at all.