MOD (Modulus) or check digit numbering involves the selection of a numbering method (MICR, Gothic, OCR, or Bar Code) to be used on documents for which an additional digit will be printed to the right of the base sequential number. Formulas are then used to verify the document sequence and information processing. This digit enables the document owner to verify and control some aspects of the document, its contents, or the intended end use of the document. The digit can be used to assure the reliability of the numeric data entered, to make sure it matches the receiver of the materials listed on the document such as situations in which medications are issued.