If you are running an E-commerce website on Shopify, you can visit their App store and search for a tool to integrate FreshBooks invoices. There are a number of tools available but Zapier (paid application) comes with many services that you might want to integrate at a later stage for your business. Zapier includes FreshBooks integration along with 500+ other popular web services. Using Zapier, you can setup Zaps which is a connector between two services and automate tedious tasks. You can also setup Multi-Step Zaps which supports Search - to avoid duplicate data and review it on your FreshBooks account. If you still have any questions regarding this, you can visit Zapier help desk here.