Three nurses and two healthcare assistants will appear in front of a judge later this month.
Between 2013 and 2015 the regulators' annual fee increased from £76 to £120 per year.
The RCN previously parted ways with the ICN in 2013 following a vote by members.
A week ago, the Government made a spectacular u-turn over mandatory vaccinations for health and social.
Health leaders have taken to social media critical of the tone of the letter.
Figures suggest there are around 40,000 unfilled registered nursing vacancies across the NHS in England.