Ok, well obviously I would BU to not pay it back....but...
I work part time, and (I'm going to round up the figures for this post) am paid £750 a month.
Last month my regular wages went into the bank, followed by another payment of £480. My wage slip (erroneously) said my hourly rate had gone up and they paid me over £1300 minus tax/NI
Wages person was away, and on return said it would be sorted out.
Yesterday I got my usual £750 in the bank, then another payment of £185. Apparently they were "supposed" to just pay me the £185, which would add to the extra they paid last month and "make it right".
Now, my employer is expecting me to pay back £750, but I think I should only pay back £185 + £480 (£665).
So, AIBU to not pay them?