HMRC Supports Millions of UK Jobs and Businesses with COVID-19 Pandemic Response Built in 4 Weeks on AWS

As the COVID-19 pandemic affected the United Kingdom, Her Majesty’s Revenue and Customs (HMRC) delivered a nationwide scalable digital solution in just 4 weeks, paying out more than £69.3 billion and supporting the income of more than 11.7 million jobs. HMRC is the department of the UK government responsible for tax collection and certain other financial administrative duties. It had been running its Multichannel Digital Tax Platform on Amazon Web Services (AWS), and it repurposed the microservices-based architecture for the purposes of COVID-19 pandemic relief. Despite unprecedented traffic, the solution achieved 90 percent customer satisfaction.

HMRC is the department of the UK government that is responsible for tax collection, some government assistance programs, and the administration of certain other regulations, such as the national minimum wage, goods declaration, statutory pay, and tax credits. Since 2017, its Multichannel Digital Tax Platform (MDTP) has been powered by Amazon Elastic Compute Cloud (Amazon EC2), which offers secure and resizable compute capacity for virtually any workload. HMRC has been providing applications for UK businesses and individuals using solutions on AWS that are scalable, resilient, and secure as it introduced personalized, digital tax accounts.

To address COVID-19 pandemic relief, HMRC sought a digital-native solution that could provide quick relief to UK employers so that they could place employees on furlough to protect their jobs. The solution had to be able to validate bank details, gauge the legitimacy of claims, and process requests quickly. Although 2.4 million employers were eligible for grants, HMRC had no way to predict actual demand. This unprecedented situation required a resilient, extremely elastic solution that could scale up automatically to an unknown level of demand and scale down smoothly once the program ended.

In early 2020, HMRC developed three services to help alleviate the financial burden of the COVID-19 pandemic on its citizens. It created the CJRS in just 4 weeks, quickly followed by the Self-Employment Income Support Scheme and the Statutory Sick Pay Rebate Scheme—which reimbursed employers for the sick pay expenses due to the COVID-19 pandemic. All relied on the MDTP microservices architecture that had been built on AWS. The digital front end took most of the load, capturing applicable information, such as company names, and feeding it to the backend systems. The backend processed electronic payments, distributing relief in fewer than 6 days.

The greatest demand was placed on the CJRS, which ended up supporting more than 11.7 million jobs in total over the program’s nearly 2-year existence. To facilitate scaling and the ability to react to unknown demand, the CJRS used Elastic Load Balancing (ELB), which automatically distributes incoming network traffic to improve application scalability. The CJRS used ELB to ingest traffic and route it appropriately to existing containers. Using AWS, the CJRS could automatically scale up to meet demand during the height of the COVID-19 pandemic using AWS Application Auto Scaling, a web service for developers and system administrators who need a solution for automatically scaling their resources for individual AWS services.

Before HMRC had created the CJRS, its MDTP had been running Amazon Elastic Compute Cloud (Amazon EC2) instances using Docker, which packages software into containers to provide a standard way to run code so that developers can build, test, and deploy applications quickly. In November 2020, HMRC began running and managing the clusters of Amazon EC2 instances in Docker at scale using Amazon Elastic Container Service (Amazon ECS), a fully managed container orchestration service.

In its first week, the CJRS processed more than 600,000 claims valued at £5 billion, as the unprecedented volume of traffic peaked at 100 requests per second. Despite HMRC’s lack of historical data from which to derive operational insights due to the unprecedented nature of the project, the CJRS ran smoothly and remained widely available to its claimants, receiving customer satisfaction scores exceeding 90 percent. In total, the program paid out more than £69.3 billion and supported more than 1.3 million employers. Plus, when the CJRS closed in September 2021, HMRC could scale down immediately so that it wasn’t left with unusable infrastructure.

HMRC’s ability to rapidly develop the CJRS and other programs at the beginning of the COVID-19 pandemic can serve as a model for how to create urgent government programs in the future. When necessary, engineers can quickly pivot the original use case for the microservices architecture in order to build and run high-performing solutions in other areas throughout the government. Most important, HMRC could fulfill its mission of supporting the UK economy and citizens’ livelihoods during the COVID-19 pandemic while maintaining public trust.