Internal control systems and procedures can ensure the accuracy and reliability of financial accounts at a business. Accounting controls are meant to ensure that the numbers being put onto the books are accurate.
Internal controls are the practices that employees are trained to do, and may be audited on, which general involve some oversight or double-checking to filter out mistakes. This not only prevents mistakes, but also malfeasance, embezzlement and fraud. Accounting done wrong can result in criminal penalties, bankruptcy, and tax problems.
Some internal procedures that can discourage or prevent mistakes include separation of duties and diffusion of responsibility among several employees, frequent documentation requirements, random audits, security measures and password protection that only gives certain employees access to certain information (and cash).