We investigate new physics effects on \(B\rightarrow D^{(*)}\tau \nu\) decays in a general and model-independent way. The \(\chi ^2\) fits for fractions of the branching ratios \(R(D^{(*)})\) and other polarization parameters are implemented. We parameterize the relevant Wilson coefficients with a new physics scale and its power together with combined fermionic couplings. Constraints from \(B_c\rightarrow \tau \nu\) are imposed such that its branching ratio is less than 30%. For a moderate range of our parameters we find that the new physics scale goes up to \(\lesssim 27~\textrm{TeV}\) for ordinary new particle contributions. It turns out that the polarization asymmetry of \(\tau\) for \(B\rightarrow D\) transition can be negative only for a few combinations of the new physics operators. We also discuss related processes \(B_c\rightarrow J/\Psi \tau \nu\) and \(\Lambda _b\rightarrow \Lambda _c\tau \nu\) decays.
