The issue of top-up payments for high earners working in health will come under scrutiny, when HSE officials appear at the Oireachtas Health Committee.
The health service has been looking into renumeration packages in publicly funded agencies.
It's understood a number of senior staff at the National Maternity Hospital are earning more than the public service pay cap.
Chairman of the Health Committee - Fine Gael's Jerry Buttimer - says some Section 38 employment contracts permit top-up payments:
