Enhanced charged Higgs boson effects in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi>B</mml:mi></mml:mrow><mml:mrow><mml:mo>−</mml:mo></mml:mrow></mml:msup></mml:mrow><mml:mo>→</mml:mo><mml:mi>τ</mml:mi><mml:mrow><mml:mrow><mml:mover><mml:mrow><mml:mi>ν</mml:mi></mml:mrow><mml:mrow><mml:mi>¯</mml:mi></mml:mrow></mml:mover></mml:mrow></mml:mrow><mml:mo>,</mml:mo><mml:mi> </mml:mi><mml:mi>μ</mml:mi><mml:mrow><mml:mrow><mml:mover><mml:mrow><mml:mi>ν</mml:mi></mml:mrow><mml:mrow><mml:mi>¯</mml:mi></mml:mrow></mml:mover></mml:mrow></mml:mrow></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>b</mml:mi><mml:mo>→</mml:mo><mml:mi>τ</mml:mi><mml:mrow><mml:mrow><mml:mover><mml:mrow><mml:mi>ν</mml:mi></mml:mrow><mml:mrow><mml:mi>¯</mml:mi></mml:mrow></mml:mover></mml:mrow></mml:mrow><mml:mo>+</mml:mo><mml:mi>X</mml:mi></mml:math>

Charged Higgs boson effects are not helicity suppressed in the decays ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\tau}\overline{\ensuremath{\nu}}, \ensuremath{\mu}\overline{\ensuremath{\nu}}, \mathrm{and} e\overline{\ensuremath{\nu}}$, and could enhance or suppress these modes without violating lepton universality. The present limit of $B({B}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\mu}\overline{\ensuremath{\nu}})&lt;2.0\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ is more stringent than the measurement $B(b\ensuremath{\rightarrow}\ensuremath{\tau}\overline{\ensuremath{\nu}}+X)=({4.20}_{\ensuremath{-}0.68}^{+0.72}\ifmmode\pm\else\textpm\fi{}0.46)%$, while a factor of 2 improvement in the present limit of $B({B}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\tau}\overline{\ensuremath{\nu}})&lt;1.2%$ would be comparable. There is much room for discovery as one pushes the latter limit down to the standard model expectation of order ${10}^{\ensuremath{-}4}$. A value below this may be explained without requiring ${f}_{B}|{V}_{\mathrm{ub}}|$ to be unduly small.