The check character, if used, is the way the symbol ensures that its data has been correctly encoded and read. Since many codes are self-checking, the check character is not required by many symbologies, although it is an option in most of them.
a character included within a symbol whose value is based, mathematically, on other characters within the symbol. It is used to perform a mathematical check to ensure the accuracy of the read. Same as checksum or check digit.
Characters added to a bar code to verify a correct read of the bar code. Check characters are usually the result of a mathematical calculation based upon the data in the bar code. Not all bar codes contain check characters.