This left just one in five organisations with “an identifiable action plan that was time-bound and included target-driven activities”.
Larger employers were found to be more likely to have an action plan in place than those with fewer than 500 members of staff.
The watchdog said it was “essential” for action plans to be produced if businesses wanted to display a real commitment to closing the divide.
Reporting laws came into force last year and the first reports revealed in April that more than three-quarters of big employers in Britain had a pay gap favouring men.
Measures to reverse the trend could include anonymising CVs and including a mixed-sex panel in job interviews, the report recommended.
EHRC chief executive Rebecca Hilsenrath said: “Earlier this year gender pay gap reporting shone a light on some of the issues women face when accessing, progressing and staying within the workplace.
“As we head towards the second year of reporting, the attention now needs to shift towards employers who must play their part in reducing the gap, starting with publicly setting out how they intend to address it in their organisation.
“Specific and time-bound action plans can do more than just identify the barriers holding women back in the workplace, they can help to create an environment where female employees can flourish, as well as demonstrate to employees, customers and shareholders a commitment to improving working practices, and can enhance the organisation’s reputation.