Re-KYC (Re-Know Your Customer) is the process of updating or re-verifying a customer's KYC (Know Your Customer) details periodically, as mandated by regulatory authorities like SEBI/NSE/BSE/RBI/NSDL/CDSL. 

Here’s why Re-KYC is necessary: 

1. Regulatory Compliance: Financial institutions must comply with legal and regulatory norms to prevent money laundering, terrorist financing, and other financial crimes. Re-KYC helps to maintain updated customer data. 

2. Updated Customer Information: Over time, customer information such as address, contact details, and identity may change. Re-KYC ensures the institution has the most up-to-date information, reducing potential risks. 

3. Risk Mitigation: It helps identify high-risk customers and transactions, ensuring that the customer data is accurate, which helps in better risk management. 

4. Prevention of Fraud: Regularly updating customer details through Re-KYC helps financial institutions detect suspicious activities and prevent fraud. 

In many cases, Re-KYC is required every 2 to 10 years, depending on the customer’s risk profile.