  We present a sequence of eight spectropolarimetric observations monitoring
the geometric evolution of the late phase of the major 2012 outburst of SN
2009ip. These were acquired with the FORS2 polarimeter mounted on ESO VLT. The
continuum was polarised at 0.3-0.8 per cent throughout the observations,
showing that the photosphere deviated substantially from spherical symmetry by
10-15 per cent. Significant line polarisation is detected for both hydrogen and
helium at high velocities. The similarity in the polarised signal between these
elements indicates that they form in the same location in the ejecta. The line
polarisation (p$\sim$1-1.5 per cent) at low velocities revealed the presence of
a highly-aspherical hydrogen and helium rich circumstellar medium (CSM). Monte
Carlo simulations of the observed polarimetry were performed in an effort to
constrain the shape of the CSM. The simulations imply that the polarimetry can
be understood within the framework of a disk-like CSM inclined by 14$\pm$2
degrees out of the line of sight, obscuring the photosphere only at certain
epochs. The varying temporal evolution of polarisation at high and low
velocities indicated that the fast-moving ejecta expanded with a preferred
direction orthogonal to that of the CSM.
