Bill.com has implemented Multi-Factor Authentication (MFA) with a "light touch" -- this security feature is unique to Bill.com.
Setting up Multi-Factor Authentication
As a part of the setup process, users will be asked to enter their phone number. Thereafter, users will be prompted with a text or voice message to enter a code in addition to their password ONLY when activity on your account catches our attention. We will prompt users to authenticate using voice or text less frequently if the "Trust this computer" box is checked. (Most users on your account will have this experience; we will not prompt approval-only users to complete this process).
Your Bill.com account is very powerful and can move money to and from the vendor and customer lists in your account. Should someone obtain the login credentials of those users on your account who have the power to change vendor and customer information, add bank accounts or make payments, you want to know that they won't be able to "do damage" by transferring your money to or from accounts where it doesn't belong. This feature helps to ensure that only the users you named on the account, with access to the phones listed during the setup process, will be able to complete actions such as these.
We've tried to implement this in such a way that it will not be a burden for you and the other users of your Bill.com account; we know most of our customers log in to Bill.com every day and don't want extra steps in their daily process. We also worked to make it a strong feature, to keep the bad guys from using your account in the wrong way.