I'm not trying to pick a fight either. But this stuff about tax is real, and I suspect your employer was either unaware of it and then suddenly got told by their admin dept or is just trying to follow the law while being confused because you are a very unusual case. I suspect they are embarrassed that they didn't pick it up earlier and are trying to "fix" the problem, figure out if they have a liability or something and then will remit your salary. Nothing in your posts suggests that you actually have anything to worry about. Had you stated that you hated your employer, that they had always dicked you around and that is why you are leaving, I might have assumed (as several other posters on here have done, with their advice) that your employer is a bastard and you should sue them/report them to the labour dept etc etc.
If my interpretation of what is going on is correct, you just need to be a bit more patient and it will all sort itself out. Surely this is a better outcome than making a fuss, being told "but we had to do this by law" or worse, having the Labour Dept tell you they had to do this by law - and burning bridges you may not have wanted to burn?
I believe there is a limit on the time the employer can hold the money. The ordinance (linked by someone else earlier) should tell you that limit and as soon as it has passed, throw the book at them.
Just don't put yourself in the position of looking silly by doing it earlier.