  Virial identities are a useful mathematical tool in General Relativity. Not
only have they been used as a numerical accuracy tool, but they have also
played a significant role in establishing no-go and no-hair theorems while
giving some physical insight into the considered system from an energy balance
perspective. While the calculation of these identities tends to be a
straightforward application of Derrick's scaling
argument~\cite{derrick1964comments}, the complexity of the resulting identity
is system dependent. In particular, the contribution of the Einstein-Hilbert
action, due to the presence of second-order derivatives of the metric
functions, becomes increasingly complex for generic metrics. Additionally, the
Gibbons-Hawking-York term needs to be taken into account
\cite{Herdeiro:2021teo}. Thankfully, since the gravitational action only
depends on the metric, it is expected that a ``convenient'' gauge that
trivializes the gravitational action contribution exists. While in spherical
symmetry such a gauge is known (the $m-\sigma$ parametrization), such has not
been found for axial symmetry. In this letter, we propose a ``convenient''
gauge for axial symmetry and use it to compute an identity for Kerr black holes
with scalar hair.
