  The gradient discretisation method (GDM) is a generic framework designed
recently, as a discretise in spatial space, to partial differential equations.
This paper aims to use the GDM to establish a first general error estimate for
numerical approximations of parabolic obstacle problems. This gives the
convergence rates of several well--known conforming and non conforming
numerical methods. Numerical experiments based on the hybrid finite volume
method are provided to verify the theoretical results.
