  Scale-dependent halo bias due to local primordial non-Gaussianity provides a
strong test of single-field inflation. While it is universally understood that
single-field inflation predicts negligible scale-dependent bias compared to
current observational uncertainties, there is still disagreement on the exact
level of scale-dependent bias at a level that could strongly impact inferences
made from future surveys. In this paper, we clarify this confusion and derive
in various ways that there is exactly zero scale-dependent bias in single-field
inflation. Much of the current confusion follows from the fact that
single-field inflation does predict a mode coupling of matter perturbations at
the level of $f_{NL}^{loc} \approx -5/3$, which naively would lead to
scale-dependent bias. However, we show explicitly that this mode coupling
cancels out when perturbations are evaluated at a fixed physical scale rather
than fixed coordinate scale. Furthermore, we show how the absence of
scale-dependent bias can be derived easily in any gauge. This result can then
be incorporated into a complete description of the observed galaxy clustering,
including the previously studied general relativistic terms, which are
important at the same level as scale-dependent bias of order $f_{NL}^{loc} \sim
1$. This description will allow us to draw unbiased conclusions about inflation
from future galaxy clustering data.
