  Rephasing invariants of quark and lepton mixing matrices are obtained in the
standard model extended by the seesaw mechanism, and in its low-energy
effective theory with the dimension-five Majorana mass operator. We classify
the basic invariants, discuss non-trivial relations between them, and determine
the independent invariants which characterize all the information in the mixing
matrices in a basis-independent way. We also discuss the restrictions on the
allowed ranges for the mixing phases, and on the rephasing invariants, which
follow from a discrete invariance of the Majorana mass matrix.
