How to make partial invoice

We are private limited company. We have taken one customisation project for which we have received 50% payment. Now we want to issue invoice for 50% payment received. Now how can we write in invoice about this 50% senario to let the customer know that this is partial invoice only. 50% invoice will be prepared after completing project. We does not want to prepare full invoice as we does not want bear tax liability. Please suggest wordings i can mention in partial invoice to let customer know that this is 50% invoice.