Under the terms of gender pay gap disclosure law, companies must publish details on the Government website and on their own websites. Until now, 11,000 businesses have complied but the deadline has now passed and offenders not to have done so could face court orders and unlimited fines.
The Equality and Human Rights Commission is tasked with ensuring that all details are disclosed.
A commission spokesperson said: "Breach of these regulations is breaking the law and we've always been clear we will enforce with zero tolerance.
“Last month, we contacted almost 1,500 businesses to commence enforcement proceedings and as a result the number of employers facing investigation is now under 500.
“The first draft terms of reference will be issued shortly and will be made publicly available in due course, as required by law.”
It is likely that when that happens businesses still not complying will be named and shamed.
The commission would not confirm the exact number of businesses it is pursuing or if any are pub related.