How do I lock Evensies with Face ID?

In Account, turn on Require Face ID. On an iPhone or iPad that unlocks with Touch ID it says Require Touch ID, and on one with neither, Require passcode. Evensies asks you to confirm it's you before the lock turns on. A phone with no passcode set has nothing to unlock with, so the switch stays off and says to set one in the phone's Settings first.

Once it's on, Lock chooses when Evensies locks again after you leave it: Immediately, After 1 minute or After 5 minutes. It always locks when it opens from scratch. Locked, it covers everything it shows, the picture in the app switcher included, asks by itself once, with Face ID, Touch ID or the passcode, and offers Unlock after that.

The choice is kept on this phone only: it isn't part of your account, isn't sent anywhere, stays through a sign-out, and each phone or iPad has its own. The demo is never locked, and neither is Evensies while nobody is signed in.

Nothing stops while it's locked: a receipt you share into Evensies from Photos or Files opens a new expense with it behind the lock, ready once you unlock. If the phone can no longer ask, because its passcode was turned off, Evensies opens rather than keep you out.