well you need time to pay the bill once the month is up.
For example, if your month ends June 5, you cant expect them to demand payment by June 5 for that month. You get a period for the bill to be sent, and basically just time between when the month is up and when the payment is due.
Late fees: $5 or 1.5% of the balance unpaid as of the next bill period (depends on which state you live (just check the second page of your monthly bill..all of this info is located there).
bigger problem is your credit is harmed with late payments....