Odoo is an open source ERP offering many modules like sales and invoice management. There is a sale management module which has invoices like draft quotations and sale orders. There are also other modules like e-invoicing,invoicing,Invoice Analysis per Company, Invoicing & Payments etc. For basic operations like sale orders, purchase orders, financial accounting, invoicing, etc, there is the option of core modules of sales, purchase and account. There are many more other modules that you can choose from. We even have created custom modules for many companies making the business process smoother for them by providing a erp system that works according to their business requirement. Odoo ERP being a opensource erp provides you with the option of choosing what you want on your platter. Implement only the modules that is most suited for your business.