  Large higher-order corrections enter the Higgs boson sector of the MSSM via
Higgs-boson self-energies. Their effects have to be taken into account for the
correct treatment of loop-corrected Higgs-boson mass eigenstates as external
(on-shell) or internal particles in Feynman diagrams. We review how the loop
corrections, including momentum dependence and imaginary contributions, are
correctly taken into account for external (on-shell) Higgs boson and how
effective couplings can be derived. The proceedures are implemented in the code
FeynHiggs 2.5.
