Change and Transformation in the Public Sector
HM Revenue & Customs (HMRC) partnered with Capgemini Invent to transform a legacy VAT mainframe into a modern, cloud based service landscape, applying user centred design and AI enabled techniques.
HM Revenue & Customs (HMRC) asked Capgemini Invent to lead one of the UK public sector’s most complex modernisation programmes: the retirement of a 50 year old VAT mainframe comprising more than 3.1 million lines of COBOL code and supporting over 80 services and 325 data feeds across critical national and international services.
Decades of attempts to retire the platform had stalled due to undocumented dependencies, operational risk and the loss of specialist knowledge. With increasing fragility, cyber exposure and escalating financial risk, modernisation had become essential.
Capgemini Invent reframed the programme from a like for like technical migration into a comprehensive transformation of VAT services. The team combined architectural leadership, AI enabled analysis and modern engineering practices to deliver cloud ready replacements for major services including the VAT Information Exchange System (VIES) and the Trade in Goods Service (TIGS), which processes over £1 trillion in annual trade data movements from customs declarations.
A key differentiator was the Model Office – an interactive environment enabling users to test prototypes, validate requirements in real time and build readiness throughout delivery. This capability was deployed at scale to support the legacy modernisation, shifting knowledge transfer from end of project activity to a continuous, embedded process.
Mobilised in October 2023, the programme reached beta in April 2025 and completed transition in December 2025 with zero disruption to critical services. The programme has set a new benchmark for user centric legacy transformation at scale across HM Government.
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