After payday

It stops you before you change a month you've paid

Turn a day into a holiday, change the weekly off days, or add holiday work or an advance in a month already marked paid, and the app stops first. It names the month, each person whose pay would move, and by how much. Payments already recorded stay as they are, so any difference shows up in Payment History instead of getting lost.

A register can't warn you. This is the mistake that causes arguments on payday, and the app catches it.