Although your contracts automatically assign to a Customer, each contract should also have a Unique Contract ID. This is a basis for an Audit Trail - each transaction should be able to be traced back to a Unique Source Document/Transaction. In this case, the contract. You could have your contract begin with the Customer ID followed by a 4 or 5 digit number sequential number. Each new contract just receives the next sequential number and attaches to the Customer ID ex: 048565-0123. This also should print on the printed contract as well.