1) Reset your password – You can reset your password by visiting http://splitwise.com/users/password_reset, or by clicking the "reset password" link on the login page of our mobile apps. Please note that only the most recent password reset email you've received will work. Each time you request a new password reset email, all previous password reset emails are invalidated as a security precaution.
2) Make sure you're using the correct email address – Sometimes people sign up for Splitwise with one email address, then try to sign in later using a different email address. If Splitwise tells you that it can't find an account for your email address, it may be because you signed up with a different email, or because you spelled your address slightly differently (for example, including vs. not including periods in a Gmail address).