Workers compensation provides protection to workers and their employers in the event of a work related injury or disease. The premiums are rated based on the business description which varies in cost depending on the risk involved. E.g. Building and Construction Trade - much higher risk and costlier than an office based employment.
For NSW employers they must have a workers compensation policy to insure themselves against compensation claims for workplace injuries if they pay more than $7,500 in wages, employ an apprentice or trainee, or are part of a group for premium purposes.