Three complementary tests of Lepton Flavour Universality (LFU) using semitauonic $B$ decays performed by the LHCb collaboration are reported. The two latter measurements are the most precise single measurements to date.They are compatible with SM prediction and with previous measurements. Using these recent LHCb results, the updated word average R(D*) and R(D) however still displays a 3.3 $\sigma$ disagreement with the SM prediction.
The D* polarization, which is a powerful complementary test of a potential LFU violation, has been measured for the first by the LHCb collaboration in two q$^{2}$ bins. This result, the most precise to date, is compatible with SM predictions and could potentially exclude some phase space regions of New Physics models where the polarization is very different from SM expectations.