  The aim of this paper is threefold. We first prove that, on
$\mathrm{RCD}(K,N)$ spaces, the boundary measure of any set with finite
perimeter is concentrated on the $n$-regular set $\mathcal{R}_n$, where $n\le
N$ is the essential dimension of the space. After, we discuss localization
properties of the unit normal providing representation formulae for the
perimeter measure of intersections and unions of sets with finite perimeter.
Finally, we study Gauss-Green formulae for essentially bounded divergence
measure vector fields, sharpening the analysis in \cite{BuffaComiMiranda19}.\\
These tools are fundamental for the development of a regularity theory for
local perimeter minimizers on $\mathrm{RCD}(K,N)$ spaces in
\cite{MondinoSemola21}.
