Whether you have an accountant in your internal team OR you do it yourself OR you have chosen to outsourced it, the financial accounting process is almost always at the center any business management system (aka an ERP system).
In ERPNext, your accounting operations consists of 3 main transactions:
Sales Invoice: The bills that you raise to your Customers for the products or services you provide.
Purchase Invoice: Bills that your Suppliers give you for their products or services.
Journal Entries: For accounting entries, like payments, credit and other types.