Perbromate is an ion. Its chemical formula is BrO4-. It contains bromine in its +7 oxidation state. It is a strong oxidizing agent. It is very unstable and turns into bromate and oxygen easily. It was first made by decay of a radioactive selenate. Later it was gotten by electrolysis of a bromate. It can also be made by oxidation of bromate with fluorine or xenon difluoride.