  We present a method for deriving bulk and edge invariants for interacting,
many-body localized Floquet systems in two spatial dimensions. This method is
based on a general mathematical object which we call a flow. As an application
of our method, we derive bulk invariants for Floquet systems without symmetry,
as well as for systems with $U(1)$ symmetry. We also derive new formulations of
previously known single-particle and many-body invariants. For bosonic systems
without symmetry, our invariant gives a bulk counterpart of the rational-valued
GNVW index $\frac{p}{q}$ quantifying transport of quantum information along the
edge.

Strongly Correlated Electrons;Disordered Systems and Neural Networks;Quantum Physics