Is the rule of not paying rent if you aren't asked for it, in the rules of Monopoly? Or is this something that people have made up? When is this ok?
According to the official rules posted at http://richard_wilding.tripod.com/monorules.htm#payingrent, property owners must ask for the rent before the player after the next player rolls the dice or they forfeit the rent.
By the official rules you must pay rent due