Breach a Hiwi (TA) contract I'm a Master's student at one of the TUs (Technical Universities) in Germany. I have been working as a hiwi ("Wissenschaftliche Hilfskraft", or Teaching Assistant) under a PhD for the past one year. 

I have signed a new contract starting from December for another six months. Can I breach the contract now? What's the procedure if I have to breach it after the contract begins?

Would it affect my job profile? Would I still be able to work in other institutes?
Short answer: Don't do it

Long answer: Breaching your contract would have legal consequences. It also will definitely not help you getting work anywhere else. Formally the fabled 'black lists' don't exist, but in general people talk to each other and someone simply breaking their contract is exceptional enough that news will spread fast. Furthermore at least in the place I was, the paperwork is often done by the universities HR-department and payment is handled through the same state agency, independent of which other institute you work at, so this will turn up as a red flag.

You can ask your boss to cancel a contract. What you want is called an "Auflösungsvertrag". However this needs to be agreed on by both sides, so you better have a good enough reason. For example as a boss, if you told me that you want to interrupt your studies to take care of a dying relative, I would gladly sign it, but if you told me you got a better offer somewhere else, I would still insist on you fulfilling the contract until I at least can find a replacement. And don't lie, as mentioned before, bad news travels fast.

Apart from this, if there is no other clause in your contract allowing you to give notice, it's best to just bear it for another six months. Document your hours, do your job diligently and wait for the time to be up. If you worked for the same boss for a year already, you knew what you were signing up for.