  For a (killed) spectrally negative L\'evy process we provide an analytic
expression for the distribution of its overshoot over a fixed level in terms of
the infinitesimal generator and the scale function of the process. Our identity
involves an auxiliary function and the simplicity of the identity depends very
much on the choice of this function. In particular, for specific choices one
recovers various previous established formulas in the literature. We review
several applications and also show that one can get in a similar way identities
of overshoots for reflected and refracted spectrally negative L\'evy processes.
