e-Billing system With over 4,000 accredited assessors, Elmhurst Energy Systems is the largest training and accreditation body in the UK for the rapidly evolving profession of energy assessment.

Elmhurst’s clients range from large organisations filing thousands of surveys each month to individuals who only file a few surveys a year. Billing such a large and varied customer base efficiently and accurately requires an automated system. Elmhurst was becoming frustrated with the lack of flexibility in its existing billing system and approached OCC to develop a replacement.


The new billing system runs as a web application on Elmhurst’s internal network, with different levels of access for the different members of Elmhurst’s accounts team. The team use the system to create and process invoices on a monthly basis. The application also provides a wide variety of reports to help support this work and gives Elmhurst staff quick and convenient access to relevant information when answering queries about customer invoices.

The calculations involved in producing the invoices are complex. Product codes must be derived from a combination of 5 different data items. Volume discounts or temporary special prices may also be applied. The system allows Elmhurst staff to configure the pricing models used, including setting up special arrangements and adding new products.


The invoices generated and emailed from the new system contain embedded links to an external website, allowing customers to pay their invoices by credit card directly from that website. A web service connects the website to the underlying database and also provides similar payments functionality internally, enabling Elmhurst staff to make payments on behalf of customers when this is preferred.

Both internal and external web pages were written in ASP.Net, while the application was written in C#. SQL Server 2005 provides the data storage.