Electrostatics/conservation of charge
Charge can be created and destroyed, as energy and matter can be created and destroyed. An instance I can think about is a positron and electron can interact to form two gamma ray photons, which have no charge. This interaction can also happen in reverse. There are many other ways for charge to be destroyed or created. In the classical sense, charge is conserved. And if your dealing with circuits, it can be considered that no charge is created or destroyed. And in most cases and almost any circuit analysis or EM theory it can be considered that charge is not created or destroyed.