BVN which stands for Bank Verification Number gives a unique identity that can be verified across the Nigerian Banking System. The Bank Verification Number is also a biometric identification system implemented by the Central Bank of Nigeria(CBN) to curb or reduce illegal banking transactions in Nigeria. It is more like a modern way of securing bank transactions, either through online banking or any other way. It is a modern security measure line with the Central Bank of Nigeria Act 1958 to reduce fraud in the banking system. On the 14th of February, The Central Bank of Nigeria through the Banker' Commitee and in collaboration with all the banks in Nigeria, launched a centralized biometric identification system for the banking system in Nigeria called BVN.

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*Benefits Of BVN(Bank Verification Number)
Bank Verification number has lots of benefits which are very relevant to all banking systems; BVN;

1.gives you a unique that can be verified across the Nigerian Banking Industry(It is not peculiar to a bank).
2.reduces fraudulent activities on a bank account.
3.gives easy access to Banking operations.
4.is accepted as a means of identification across all Nigerian Banks.
5.makes the bank account to be protected from unauthorized access.
With the BVN query service, anyone can now check his/her BVN (Bank Verification Number) using a mobile phone without the need of going to the bank or ATM. To check the BVN number on your mobile phone, you are going to use the USSD code. USSD stands for Unstructured Supplementary Service Data, they are sometimes referred to as "Quick Codes or Feature Codes". It is a communications protocol used by GSM cellular telephones to communicate with the mobile network operator's computers. Using the USSD code doesn't require any data connection or internet. Just open your dialer and dial *565*0# and NIBSS returns the BVN associated with the mobile number. Now the next step is to link your BVN with your existing Bank account(s) in Nigeria. This code works for all banks(Zenith bank, Access bank, Fidelity bank, First bank, Eco bank, Skye bank, WEMA, Sterling bank, Keystone bank, Stanbic IBTC bank, Skye bank, Enterprise bank, Jaiz bank, UBA, Diamond bank, Unity bank, Union bank) and it works for all networks(Airtel, MTN, Glo and 9mobile) in Nigeria. You will be charged N20 per USSD dialed.
*How to enroll for BVN(Bank Verification Number) in all banks
1.Go to any bank of your choice;
2.Request, fill and submit their BVN enrollment form;
3.Present yourself for capture(Fingerprint, Photo etc.);
4.A transaction slip and a transaction ID will be issued to you right away;
5.In less than a day, you should receive a text message indicating your new BVN. You can now link your BVN with your bank accounts.

https://www.foxxtek.com.ng/2018/04/how-to-check-your-bvn-number-using.html