Find out from the above links where you can get an initial legal consideration of your position. It maybe a good idea to have legal insurance, as this may drag on a bit. It's not likely that your issue will be dealt with in 15 minutes; be prepared to pay CHF60 or so for a 'first hour' consultation, which will allow your advisor more time to consider the angles.

One very effective approach to inflict damage - if that's your want - is to approach the Tax authorities and declare your income, even if you're taxed at source. Go in the light of transparency and say you just want to be sure you don't owe any more tax based on the earnings your ex-employer obviously didn't register. Bring along copies all the documents you have given to the lawyer.

They'll look into it if they feel there's been fraud, and you'll have a positive relationship with the Tax department, which is no bad thing. It would make your ex-employers life a little less comfortable, the idiot.

The arbeitsgericht are hopeless for complex issues. My advice is get yourself a basic consultation with the big boys and follow their advice.

What goes around, comes around.