You must set up a Zoho username and password to sign in to the iPhone/Android apps. Here's how you do this:

• visit https://accounts.zoho.com/password.
• Specify your Google email address or the Yahoo email address in the "Enter your registered email address" field. Please make sure that you enter the email address as 'email@gmail.com/email@yahoo.com'. Verify the image.
• Click the Request button.
• You will receive an email shortly to your Google/Yahoo email address, with the link which directs you to setting up a password.
• Move on to your iPhone/Android device and access Zoho invoice. Enter your username and password to sign in.