  We investigate the flavour-changing neutral current decay of the lightest
stop into a charm quark and the lightest neutralino and its four-body decay
into the lightest neutralino, a down-type quark and a fermion pair. These are
the relevant stop search channels in the low-mass region. The SUSY-QCD
corrections to the two-body decay have been calculated for the first time and
turn out to be sizeable. In the four-body decay both the contributions from
diagrams with flavour-changing neutral current (FCNC) couplings and the mass
effects of final state bottom quarks and $\tau$ leptons have been taken into
account, which are not available in the literature so far. The resulting
branching ratios are investigated in detail. We find that in either of the
decay channels the branching ratios can deviate significantly from one in large
parts of the allowed parameter range. Taking this into account, the
experimental exclusion limits on the stop, which are based on the assumption of
branching ratios equal to one, are considerably weakened. This should be taken
into account in future searches for light stops at the next run of the LHC,
where the probed low stop mass region will be extended.
