What does this mean?
Within the next year under new legal requirements anyone employing 250 people or more will have to publish their gender pay gaps.
The move is to attempt to fight against workplace discrimination.
Public, private and voluntary firms will all have to disclose gender pay gaps as well as any bonuses.
Around half of the UK workforce will be affected by the new rules.
Firms will have to publish a snapshot of their employee pay as of April 5 2017, this is if its a private business or charity, this is the 31 March for those in the public sector.
Some firms have already published their figures such as Virgin Money and Deloitte. All data will eventually be put into a central government database.
Any companies who do have a gender pay gap will have to publish an action plan alongside the figures to resolve the issue.
Emma Codd from Deloitte UK, said: “Today sees a big step forward in the journey to achieve gender parity in the UK,”
“For the first time people will be able to see the gender pay gap of large employers at one fixed point in time, with this gap measured and reported in a consistent way.”