SMS-based OTP is one of the most user friendly multi-factor authentication mechanisms today that does not require an additional device. The security of the web is a very important issue, because every day we make a variety of operations on the web. Apart from protecting the information, contacts, accounts and data on the web, such data should be inaccessible to third-party persons. The project examined the design and implementation of a two-factor authentication login system using OTP with SMS. A transaction authentication number (TAN) is used by some online banking services as a form of single-use, one-time passwords (OTPs) to authorize financial transactions. TANs are a second layer of security above and beyond the traditional single-password authentication. TANs provide additional security because they act as a form of two-factor authentication (2FA). The researcher delved into developing a more secured login application that sends a secret passcode to the registered phone number of a user for identification purpose. The theory of computation is also concerned with finding the most efficient methods for solving specific problems. The aim of the application is basically to ensure that users are safe, and all logins are authorized. In conclusion, by introducing the Two-Factor Authentication (PIN and SMS Password) method in our banking sector and then making it a matter of choice (not mandatory) for ATM users, banks in Nigeria will optimally deliver their services at acceptable levels of security. Ensuring the security of financial transactions will drive our banking sector to a whole new level of quality of service.