It was a massive undertaking. The existing billiing system had been in place for nearly 30 years. It was all custom code, developed incrementally over the life of the system by multiple teams of internal staff. The system served two major departments of L&S Industries and each month delivered bills to nearly a half-million clients.
The project which finally produced a modern replacement system stretched over nearly five years and, at its peak, probably had nearly 100 people involved. Most such projects do not succeed. This one did. If you are interested in more of the story, it can be found in the attached .pdf file. Just click on the title above.