Asking for a friend as I really don't know, but this just doesn't sound right to me!
She's been with the same employer for a number of years. Moved internally around 6 years ago to a different location, but with the same firm doing the same job.
Technically salary for new location was lower, but as this move wasn't requested by her, but insisted upon my management to help them out, they adjusted her salary so that the basic was reduced, but she received a monthly "supplement" (this is how it appears on payslip) so she didn't lose out financially.
New management has now said this should never have happened and are saying they're taking it away. This is a reasonable sum which she cannot afford to lose.
Surely they can't just do this?