  It is generally thought that the light coming from the inner plunging region
of black hole accretion discs contributes negligibly to the disc's overall
spectrum, i.e. the plunging fluid is swallowed by the black hole before it has
time to radiate. In the standard disc model used to fit X-ray observations of
accretion discs, the plunging region is assumed to be perfectly dark. However,
numerical simulations that include the full physics of the magnetized flow
predict that a small fraction of the disc's total luminosity emanates from the
plunging region. We investigate the observational consequences of this
neglected inner light. We compute radiative transfer based disc spectra that
correspond to 3D general relativistic magnetohydrodynamic simulated discs
(which produce light inside their plunging regions). In the context of black
hole spin estimation, we find that the neglected inner light only has a modest
effect (this bias is less than typical observational systematic errors). For
rapidly spinning black holes, we find that the combined emission from the
plunging region produces a weak power-law tail at high energies. This indicates
that infalling matter is the origin for some of the `coronal' emission observed
in the thermal dominant and steep power-law states of X-ray binaries.
