siwapp is a Web application meant to help manage and create invoices in a simple, straightforward way. It can manage invoices with different serial numbers (as rectification invoices), provide printable PDF versions of the invoices with a professional look & feel, save drafts of your invoices and continue editing them later, and automatically generate invoices on a periodic basis.
MEVEO is a billing system for mediation, rating, invoicing, payment, dunning, and composition. It is adapted to the following situations: batch processing of thousands of invoices per month (or much more), complex price plans, real time rating, and re-rating, automatic provisionning through an API, multi-format CDRs, and pre/post-invoicing reports.
Konik provides an easy way to create, read, and validate ZUGFeRD invoices. It features an easy and understandable API, extensive documentation with examples, logical invoice validation with JSR303, validation of invoices against ZUGFeRD profiles, validation of invoices against specific country invoice regulations, easy invoice appending or extracting in and from PDFs, and multiple PDF Carriages from different vendors.