If your clients don’t require receipts you can skip the production module altogether. If you want, you can still input receipts in the production phase to help manage your budget, but then when you want to submit your final invoice, you can go back to your estimate window and generate a invoice from this stage, skipping the production phase altogether. If you do not have line items currently in your invoice window, it will appear as start invoice. If you have line items already in your invoice, it will appear as overwrite invoice. If you choose to overwrite, it will replace line items that are in your current invoice with the line items in your estimate phase. You must be sure that overwriting is what you want to do because you cannot revert back to what you had in your invoice once you overwrite.