Invoice Digitisation


A client that provides procurement services for over 300 NHS trusts required integration between a multi-instance ERP system and a new invoice digitization platform. Reliability, availability and performance were the key benchmarks of this project.

Project Objectives

The high-level objectives of the project were:

● To deliver the integration solution within six weeks
● Minimise costs, including licensing fees
● Ensure the solution was able to meet an SLA of 99.9% uptime as a minimum
● Ensure that invoices were not lost during processing as this would result in suppliers not being paid
on time
● Show the status of every invoice processed by the middleware
● Provide a streamlined mechanism to deal with processing exceptions created by the legacy
solution, and minimise the support needed by reducing the number of invoices requiring manual
intervention from around 35% to less than 1%

Benefits and Risks


Business continuity was paramount for the new solution, since system downtime could result in a large backlog of invoices and payment delays to suppliers. The solution was therefore designed to be highly available and capable of tolerating multiple failures while still meeting its stated objectives. The high rate at which invoices were processed by the new invoice digitization platform posed the risk of overwhelming various downstream systems capable of lower throughput. The solution was designed to flex with the incoming load and tuned to process transactions at a consistent rate, matched to the capacity of downstream systems.


Process analysis and resourceful design delivered a system that cut licensing costs by half compared to the solution preferred by the integration platform vendor. The solution performed at many multiples of the target throughput. Even in the event of a failure, the built-in redundancy delivered well in excess of minimum requirements, without any significant tuning activity. Each redundant instance of the integration solution was capable of processing around 25 million transactions per day compared with the 10 million transactions target.


Project Scope and Approach

The new scanning platform created a digital copy of every paper invoice, expressed as XML documents, which were stored in the platform along with metadata about each invoice.

The integration layer retrieved a list of unprocessed invoices, splitting it into individual records and queuing them on a message broker, ensuring that no invoices were lost. A network of message brokers was used to provide high availability and reliability.

Each invoice underwent a number of processing steps including:

● Interactions with external systems to verify the state of the invoice
● Obtaining and storing the invoice and its metadata in storage local to the integration platform
● Enrichment of the invoice using data from external systems by adding data and altering the structure
of the original invoice
● Validation the invoice to ensure all required fields were present
● Transformation of the invoice into a canonical structure suitable for consumption by the ERP
● Dynamically route the invoice to one of a number of ERP system instances based on the content of
the invoice
● Post the invoice into the correct ERP system instance
● Update the scanning platform with the processing status of each invoice



The functional and non-functional requirements were all delivered as specified, providing a reliable, highly available solution that provides excellent performance and can scale with the business. The desired licence fee savings were realised and the solution itself utilised some open source components that further reduced licensing costs.

Third Republic