@bhussey It’s a very broad question. 

Customization allows you to write C# code, so theoretically you can do whatever. But of course there are some limitations. E.g. access to the platform itself is restricted. But you can modify most of the business logic of the application, create new forms, processes, etc.

As for building an app outside of Acumatica and integrating it via APIs, we have several different APIs. Contract Based REST API is one of them. It exposes most standard objects via API. They way you interact with the objects in the system is much less flexible than if you access it from within the system via customization, but at the same time it’s much easier to build. 

Hope that helps. If you have some specific question in mind, let us know. 

Thanks, we have a lot of legacy information in our current erp that we wouldn’t want to necessarily import but would like the users to be able to view the information (order, product info, etc). Does acumatica allow you to access external databases?

@bhussey not out of the box. You can connect it to an external DB using standard C# mechanisms and show the custom data on a separate screen. That does require creating this screen and writing C# code. And you’ll not be able to show it on the same form as the new documents.