Can liquidated damages in the case of breach of contact automatically be collected as debt? Or does it have to be proved first?

  If I understand you correctly, you're asking if you can collect damages for breach of contract without first getting a Court to issue a judgment.  The answer is no.  First, while you claim that the other side breached the contract, the other side no doubt tells a different story; if you can't resolve your differences, a court will have to decide.  Second, there are several legal requirements which liquidated damages provisions must meet to be enforceable.  A court may decide that, even though the other side breached the contract, the liquidated damages provisions in your contract are unenforceable, and then you would have to prove your actual damages.