when a contract is deemed void it s as if the contract never existed legally speaking hence anything you did under the void contract is generally not recoverable and you can t seek restitution however it s best to consult with a legal professional about your particular situation to understand the possible remedies open to you 
the bottom line void is the legal term for a contract that cannot be enforced this may be because the original contract contained aspects not allowable under the law a contract may also be considered void if the terms are vague or impossible to perform 