In this talk I review the status of new physics in b→cτν transitions in the EFT framework of dimension-six operators. The fit results, including the recent measurement of FL(D*), are presented for all one- and two-dimensional scenarios resulting from the tree level exchange of a single new particle. Particular emphasis is put on the constraint from the Bc→τν decay rate. I introduce a sum rule for the branching ratios of B→Dτν, B→D*τν and Λb→Λc τν which holds for any NP contribution to the Wilson coefficients and predicts an enhancement of the latter decay w.r.t. the Standard Model. I also discuss correlations between the polarisation observables in B→Dτν, B→D*τν and their model-discriminating prospects. The talk is based on the results published in https://arxiv.org/abs/1811.09603.