Jersey's States Employment Board is revoking a pay rise given to 126 health professionals and social workers, after a report said their pay grades had been "inappropriately uplifted".
The roles were evaluated in November 2017 and the pay grade and salaries of the staff were increased.
However, the States says that the evaluation process that was used to offer the pay rise was outside of of the recognised process used for other roles, which it says sparked nurses and midwives to say that the process was unfair.
As a result, the health department says it commissioned an independent review at the request of the unions.
The report concluded that the pay evaluation process was flawed and so those who saw a pay increase last year will be returned to their original pay grades in April 2019.
The States says it has written to all employees affected.