  We construct a double null coordinate system $(u,v,\theta_\star,\phi_\star)$
for Kerr-Newman-de Sitter spacetimes and prove that the two-spheres given by
the intersection of the hypersurfaces $u=\mbox{constant}$ and
$v=\mbox{constant}$ are $C^\infty$ in Boyer-Lindquist coordinates (including at
the "poles"). The null coordinates allow one to immediately extend some results
previously proven for Kerr. As an example, we illustrate how Sbierski's result,
for the wave equation on the black hole interior, for Reissner-Nordstr\"{o}m
and Kerr spacetimes, applies to Kerr-Newman-de Sitter spacetimes.
