  We investigate the conditions on the Higgs sector that allow supersymmetric
SO(10) grand unified theories (GUT) to break spontaneously to the standard
electroweak model (SM) at the renormalizable level. If one considers Higgs
representations of dimension up to the adjoint, a supersymmetric standard model
vacuum requires in most cases the presence of non-renormalizable (NR)
operators. The active role of Planck induced NR operators in the breaking of
the gauge symmetry introduces a hierarchy in the mass spectrum at the GUT scale
that may be an issue for gauge unification and proton decay. We show that the
minimal Higgs scenario that allows for a renormalizable breaking to the SM is
obtained by considering flipped $SO(10) \otimes U(1)$ with one adjoint ($45_H$)
and two pairs of $16_H \oplus \bar{16}_H$ Higgs representations. We consider a
non-anomalous matter content and discuss the embedding of the model in an $E_6$
grand unified scenario just above the flipped SO(10) scale.
