  We aim to study the temporal and spectral behaviour of \vum from the optical
to the X-ray regimes. We used archival \xmmn and \tes observations obtained in
2017 and 2019 to perform a spectral and timing analysis of the highly variable
polar. The light curves of both satellites, TESS and XMM-Newton, reveal a
double-humped pattern modulated with the periodicity of $91.058467 \pm 0.00001$
minutes. V496 UMa displays a two-pole accretion geometry in the high accretion
state. X-ray spectra from both regions are composed of thermal plasma radiation
and soft blackbody components with almost identical temperatures and a total
accretion rate of $\dot{M}=1.4(8)\times10^{-11}$ M$_{\odot}$ yr$^{-1}$. The
X-ray centers of the humps show longitudinal shifts of -18 and 4 degrees and
-172 and -186 degrees size around photometric phase zero, for the main hump and
second hump, respectively. The long-term ZTF light curves reveal high and low
accretions states. Low-state ZTF and SDSS photometric data are consistent with
an $0.8$ M$_{\odot}$ white dwarf at 10000 K and a main-sequence donor star with
a spectral type of M5.0 at a \gai-determined distance of 758 pc. V496 UMa is a
very bright polar in X-rays when it is in the high state. Due to its unusual
geometric structure, mass accretion onto the second accretion pole is
interrupted occasionally. This discontinuous behavior does not follow a certain
pattern in time and is observed so far only in the high state. The X-ray light
curves display clear evidence for an accretion stream at the photometric phase
of $\phi=$0.81, which does not show up in optical light curves. An accurate
period was derived using the combined TESS and XMM-Newton data, which differs
by 3.8 $\sigma$ from published results.
