The technical and practical hurdles companies face in calculating their gender pay gap is about to become a reality when the report on the topic becomes mandatory for many businesses.

ACAS has teamed up with the Government Equalities Office to publish the guidance and all employers with a head count of 250 or more will have to provide a salary snapshot of male and female employees, covering mean averages, bonuses and more.

The pressures on HR departments for this is challenging for they must produce formulas which prove not only how, but why they use the calculations they do to report on and by extension, ensure parity in pay for both sexes.