  We consider the decay of a neutral Higgs boson of arbitrary CP nature to a
massive quark antiquark pair at next-to-next-to-leading order in perturbative
QCD. Our analysis is made at the differential level using the antenna
subtraction framework. We apply our general set-up to the decays of a CP-even
and CP-odd heavy Higgs boson to a top-quark top-antiquark pair and to the decay
of the 125 GeV Higgs boson to a massive bottom-quark bottom-antiquark pair. In
the latter case we calculate, in particular, the two-jet, three-jet, and
four-jet decay rates and, for two-jet events, the energy distribution of the
leading jet.
