Simple Invoice Manager is a php based web app to manage your invoices/ payments/ quotations/ customers. You can call this open & responsive invoice management solution. User Interface is very easy and simple. There are 2 user levels, admins and sales. Reports including Daily Sales, Monthly Sales and Custom search invoice/payment reports. Settings menu to change logo sand update other settings easily.
Demo: https://codecanyon.net/item/simple-invoice-manager-invoicing-made-easy/4259689