Overdue chores appear on ChoreMonster with an orange circle around it and an exclamation point next to it.
A chore will become overdue once it's past its due date. It will remain overdue until the next instance of the chore occurs. So an everyday chore won't ever appear as overdue but and every other day chore or a bi-weekly chore could show up as overdue.
The only way to remove overdue chores (besides marking them as complete) is the skip function in the Mothershp app. If you navigate to the 'chores' tab on Mothershp and click the gray square to the right of the chore a new menu will appear with three new options; copy, delete and skip. The skip option will get rid of this chore from the child's view.