  Vertical charge order shapes the electronic properties in layered charge
density wave (CDW) materials. Various stacking orders inevitably create
nanoscale domains with distinct electronic structures inaccessible to bulk
probes. Here, the stacking characteristics of bulk 1$T$-TaS$2$ are analyzed
using scanning tunneling spectroscopy (STS) and density functional theory (DFT)
calculations. It is observed that Mott-insulating domains undergo a transition
to band-insulating domains restoring vertical dimerization of the CDWs.
Furthermore, STS measurements covering a wide terrace reveal two distinct band
insulating domains differentiated by band edge broadening. These DFT
calculations reveal that the Mott insulating layers preferably reside on the
subsurface, forming broader band edges in the neighboring band insulating
layers. Ultimately, buried Mott insulating layers believed to harbor the
quantum spin liquid phase are identified. These results resolve persistent
issues regarding vertical charge order in 1$T$-TaS$2$, providing a new
perspective for investigating emergent quantum phenomena in layered CDW
materials.
