  We explore scenarios where the $R(D^{(*)})$ anomalies arise from semitauonic
decays to a right-handed sterile neutrino. We perform an EFT study of all five
simplified models capable of generating at tree-level the lowest dimension
electroweak operators that give rise to this decay. We analyze their
compatibility with current $R(D^{(*)})$ data and other relevant hadronic
branching ratios, and show that one simplified model is excluded by this
analysis. The remainder are compatible with collider constraints on the
mediator semileptonic branching ratios, provided the mediator mass is of order
TeV. We also discuss the phenomenology of the sterile neutrino itself, which
includes possibilities for displaced decays at colliders and direct searches,
measurable dark radiation, and gamma ray signals.
