  Experimental measurements of $R_{D}$, $R_{D^*}$ and $R_{J/\Psi}$ in $B \to
(D,\,D^{\ast})l\nu$ and $B_c \to J/\Psi l \nu$ decays mediated via $b \to
c\,l\,\nu$ charged current interactions deviate from standard model prediction
by $2.3\sigma$, $3.4\sigma$ and $2\sigma$, respectively. In addition, a
deviation of $1.5\sigma$ from the standard model prediction has been witnessed
in $\mathcal B(B \to \tau \nu)$ mediated via $b \to u\,l\,\nu$ charged current
interactions as well. Motivated by the anomalies present in $B$ and $B_c$ meson
decays, we analyze the corresponding $B_s \to (K,\,K^{\ast})\,\tau\,\nu$ and $B
\to \pi\tau\nu$ semileptonic decays within the standard model and beyond. We
use an effective field theory formalism in which $b \to c$ and $b \to u$
semileptonic decays are assumed to exhibit similar new physics patterns. We
give the predictions of various observables such as the branching fractions,
ratio of branching ratios, lepton side forward backward asymmetry, lepton
polarization fraction and convexity parameter for $B_s \to (K,\,K^{\ast})\tau
\nu$ and $B \to \pi\tau\nu$ decay channels within the standard model and within
various NP scenarios.
