A CIN number, or Corporate Identification Number, is a unique identification number assigned by the Registrar of Companies (ROC) to companies registered in India. It is a 21-digit alphanumeric code that is issued to companies at the time of their registration and is mentioned in their registration certificate. The CIN is used to track all the activities and other aspects of a company, right from its incorporation. It is an important number as every company must mention this unique CIN in the forms to be submitted to the Ministry of Corporate Affairs (MCA), particularly in audits and reports. The CIN can be used to identify or track companies for several levels of information that ROC/MCA holds. The CIN contains important details such as the year of incorporation, state code, type of company, and ROC code of the company.