Top Legacy Software Modernization Companies in Europe: A Full Guide for 2027

The UK government’s State of Digital Government Review put legacy systems at 28% of central government department estates in 2024, up from 26% a year earlier.

Inside your own company, the same pattern shows up as an ERP extension written in VB6, a pricing engine on .NET Framework 4.x, and a nightly batch job one engineer understands. Each piece still earns money, so switching it off is not an option, and each one holds back the cloud, data, and AI projects queued behind it.

In this article, we’ve prepared the top legacy software modernization companies in Europe for 2027, with the core information you need to make a decision. Also, you’ll find the numbers behind the modernization, the phases a live migration moves through from audit to cutover, and 5 checks to run on any partner before work starts.

TL;DR

• Live migration moves through audit, dependency mapping, pilot, parallel run, and cutover, in that order.
• Legacy stacks named on a vendor’s own pages show what that team has migrated before.
• AI-assisted refactoring speeds up code conversion, with engineers reviewing each change before release.
• Parallel runs on live transactions catch behavior gaps before customers see them.
• Questions about rollback, data reconciliation, and knowledge transfer reveal how a partner handles risk.
• List of top legacy software modernization companies in Europe includes Reenbit, Future Processing, Intellias, Sigma Software, Spyrosoft, Endava, itemis.

Spending, Support Dates, and Rules Shaping Modernization in 2027

Deadlines shape modernization budgets in 2027 as much as ambition does. Support windows close on widely used platforms, regulation cuts the cost of leaving a cloud provider, and overall IT spending keeps rising, so the timing of your project matters as much as its scope.

Money is flowing into technology at a fast pace. Gartner forecasts worldwide IT spending at $6.37 trillion in 2026, growth of 14.2%, with software spending up 15.5% to $1.47 trillion, according to the forecast it released in July 2026. More of that budget now goes to platforms that legacy systems struggle to connect with.

Company size still decides how much software a business runs. Eurostat data published in May 2026 shows ERP software in use at 41% of small EU enterprises with 10 to 49 employees and 89% of large ones with 250 or more in 2025. For a growing company, the move from spreadsheets and older tools to a proper ERP often arrives together with a wider modernization.

Support dates add hard deadlines. Microsoft ends support for .NET 8 and .NET 9 on November 10, 2026, and the .NET team confirmed that no new security updates will follow for applications still running on either version. Regulation pushes in the same direction: Article 29 of the EU Data Act bans cloud switching charges from January 12, 2027, and limits any charge between January 11, 2024, and that date to costs linked directly to the switch.

The public sector shows what happens when old systems stay in place too long. In the UK, the State of Digital Government Review rated 22% of assessed central government legacy systems red, meaning high risk likelihood and high impact, and put their upkeep at 3 to 4 times the cost of modern alternatives. Your business faces the same arithmetic on a smaller scale.

List of the Top Legacy Software Modernization Companies in Europe

Modernization partners rebuild, re-platform, or retire old software while operations continue on the existing system. We’ve prepared 7 of them, describing how they line up on expertise, their security certifications, and engagement models:

Reenbit

• Founded: 2018
• Services: .NET modernization, cloud-native re-architecture, database migration, Azure cloud migration, DevOps and CI/CD, AI-assisted modernization
• Industries: Manufacturing, construction, healthcare, retail, fintech, energy, facility management

Reenbit is a top legacy software modernization company in Europe for growing companies that can’t pause operations to rebuild. Work opens with an Assessment Sprint of 1 to 2 weeks that maps the legacy system, its constraints, and technical debt, then closes with a modernization roadmap and a call on whether to rebuild, re-architect, or refactor. Delivery follows in phases, so the existing platform keeps serving users through the migration.

As an AI-powered technology consultancy and Microsoft Partner, Reenbit runs a team of 100+ engineers, with 88%+ of them holding Microsoft or Azure certifications, and 75+ projects shipped over 8+ years. ISO 27001:2022 certification and GDPR-compliant builds with data residency on Azure support clients in regulated sectors. Results on modernized systems include up to 30% lower cloud costs, up to 40% less manual processing, and 99.9% uptime, and 23 verified Clutch reviews point to transparent communication and predictable delivery.

Future Processing

• Founded: 2000
• Services: Rehost, replatform, rearchitecture, rewrite, experience enhancement, post-M&A systems merge
• Industries: Insurance, finance, transport, technology, media, manufacturing, construction, healthcare, nonprofit

Future Processing ties application modernization to business outcomes, with written value guarantees and tactical quick wins within 4 weeks. Commercial terms follow a pay-only-for-performance model backed by a money-back guarantee, and fees drop when the work misses agreed objectives. Legacy and new systems can run side by side during migration.

One marine insurer is replacing a 45-year-old COBOL core with .NET, and another insurance client cut onboarding from 6 months to 2 weeks while doubling team velocity. Alongside that, the firm holds AWS Advanced Tier Services Partner status and has worked as a Microsoft Partner since 2007.

Intellias

• Founded: 2002
• Services: Application landscape rationalization, technical debt assessment, cloud readiness and TCO assessment, legacy system modernization, cloud migration, data migration
• Industries: Mobility, financial services and insurance, retail, healthcare and life sciences, iGaming, high-tech

Intellias centers modernization work on mainframe exit and cloud migration, with IBM i, IBM z, UniVerse, and VMware among the platforms in scope. Projects move through Ignite, Reinvent, and Accelerate phases. That sequence supports progressive portfolio modernization with zero-downtime deployments.

City Plumbing left a mainframe core behind, with 300+ workloads shifted to AWS, 99.999% availability, 30% lower infrastructure costs, and 39% revenue growth. A telecom client cut costs by 30% after 60+ BSS apps moved to a multi-cloud environment. Partnerships cover AWS Advanced Consulting Partner, Microsoft Solutions Partner, and OpenAI Select Partner status.

Sigma Software

• Founded: 2002
• Services: Technology consulting, technology modernization, migration and re-platforming, software re-engineering, UI/UX modernization, DevOps and infrastructure
• Industries: AdTech, automotive, aviation, construction and real estate, defense, energy, finance, healthcare, manufacturing, logistics, telecommunications

Sigma Software has delivered dozens of legacy transformation and migration projects, including 30 modules moved from FoxPro to .NET for a real estate ERP vendor. The Mikz platform reached 5x lower infrastructure costs on Azure, and an airline budgeting replacement cut IT costs by 50%.

Teams scale from a single full-time developer to a dedicated group of 5 to 10 experts or a development center of 20+. SAS reached a 50% cost reduction 2 years ahead of plan, and Siemens saw 15+ years of historical data migrated. Ownership sits with Danir AB.

Spyrosoft

• Founded: 2016
• Services: Infrastructure modernization, UI/UX redesign, data warehouse analysis, process optimization and automation, managed services, IT systems takeover
• Industries: Financial services, automotive, healthcare and life sciences, Industry 4.0, media and entertainment, retail, public sector, and 12 more

Spyrosoft runs legacy modernization for financial services through a dedicated financial system modernization offer that tackles priority improvements first. Managed services follow ITIL and the AWS Migration Acceleration Program, including the Migrate and Modernise track.

Engagements can follow a Build Operate Transfer model, with a build stage of 1 to 3 months, operation for up to 3 years, and a transfer of up to 3 months. Fixed-price projects and time-and-materials services sit next to that model. The group employs 2,000+ experts, serves 300+ clients, and went public on the stock exchange in 2022.

Endava

• Founded: 2000
• Services: Landscape and system assessment, strategy and roadmap, transformation in execution, core modernization run and evolve, core modernization assets
• Industries: Automotive, energy, finance and banking, government, healthcare, insurance, payments, retail, logistics, telecommunications, travel

Endava modernizes legacy systems into a flexible digital core, with agentic AI virtual SMEs supporting assessment and delivery. Published totals cover 100+ clients, 300+ systems, and 500 million+ lines of code analyzed.

Assessment work includes a technical debt review for a major investment bank and a review of a legacy operations system for an airline. Modern Managed Services cover operations once delivery ends, and SOC 2 Type II attestation arrived in January 2026. A Cognition partnership signed in February 2026 extends agentic coding across engineering work. Headcount stood at 11,365 in a May 2025 filing.

itemis

• Founded: 2003
• Services: Legacy modernization, AI enablement, full-stack and cloud, model-driven software development, toolchain integration
• Industries: Banking, insurance, logistics, energy, public sector, industry

itemis migrates legacy systems written in COBOL or PL/I to modern architectures with readable, provably correct code. A five-stage model moves from deterministic transpilation to test generation, AI-assisted documentation, an MCP-server tool, and spec-driven refactoring, with human review of every AI output and the strangler fig pattern for cutover.

Société Générale moved core banking to the cloud across 10 million lines of code and 17,000 programs at a 99.99% automation rate. Zurich Group saw about 200,000 lines of C moved into a domain-specific language, removing up to 4 weeks of manual work per release.

Phases the Top Legacy Software Modernization Companies in Europe Run on Live Systems

A modernization that keeps the business running follows a fixed order, and skipping a phase pushes its risk into the next one. Here are the 5 phases in the order your team will meet them:

Phase 1. Audit the Estate Before Anyone Writes Code

The audit inventories every application, database, integration, and scheduled job, then records who owns each one and what it costs to run. Depending on how much documentation survives, this step can take several weeks.

Your output is a single map of the estate, scored by business value and technical risk. That map decides which modules move first and which ones stay put for now.

Phase 2. Map Dependencies and Hidden Business Rules

Dependency mapping turns the audit into a migration order. Here is what your team needs on paper before the first module moves:

• Call graphs between services, stored procedures, and batch jobs, traced from production logs over a full business cycle.
• Business rules extracted from code and confirmed in writing by the finance and operations staff who rely on them.
• External integrations listed with owner, protocol, and contact, including file drops and partner APIs the audit missed.
• Data lineage for every table that feeds reporting, billing, or regulatory submissions, with the system of record named.

Phase 3. Pilot One Module With Real Traffic

A pilot proves the target architecture on one bounded module, usually a service with clear inputs, clear outputs, and moderate traffic. Your team learns the deployment pipeline, the monitoring, and the rollback drill on something small enough to fix fast. Good pilot candidates include:

• Notification and email services
• Document generation
• Reporting read models
• Customer self-service portals
• Pricing calculators with stable rules

Phase 4. Run Old and New Systems in Parallel

Parallel running sends the same live inputs through both systems and compares what comes out. Here is how you keep that phase under control:

• Output comparison. Automated diffs flag every mismatch in totals, statuses, and documents within the same day.
• Sync monitoring. Scheduled reconciliation jobs run against both databases, and alerts go to a named owner.
• Exit thresholds. A written mismatch rate decides when the new system takes full traffic.
• Cost tracking. Both platforms bill at once, so the phase gets a fixed end date in the plan.

Phase 5. Cut Over and Retire the Legacy Platform

Cutover moves the last traffic to the new system during a planned window, with the rollback route kept warm for a set period afterward. A rollback rehearsal in the week before cutover tells you whether that route works under load.

Retirement comes last: archive the data your regulators require, cancel the old licenses and hosting, and remove the legacy code from the repository. Until those 3 steps finish, your business keeps paying for both platforms.

How to Choose a Modernization Partner for Your Business

Modernization proposals often list the same headline services. Delivery details show how each partner handles a live system. Here are the 5 points to get in writing:

• Published stack history. Ask for named projects on the exact stacks in your estate, such as .NET Framework, VB6, or COBOL, with the year each one shipped.
• Assessment deliverable. Request a sample report from a past audit, so you see the dependency map and risk scoring your own estate would receive.
• Rollback plan. A strong answer explains how traffic returns to the old system if the new one fails, and how often your team will rehearse that switch.
• AI usage terms. Confirm which AI tools touch your code, where they run, and who reviews the output before it reaches production.
• Knowledge transfer. Agree on documentation, pairing, and a handover date, so your engineers can run the new platform without the vendor on call.

Final Thought

Legacy software modernization moves the systems that bill customers, ship orders, and pay staff onto platforms with a future. The trouble sits in timing: support deadlines and regulatory dates arrive on fixed days, while the old code holds rules and data nobody has fully catalogued. Left without an owner, that gap turns into emergency support fees, a frozen roadmap, and engineers who spend the year on upkeep.

Picking from the top legacy software modernization companies in Europe settles more than the next 12 months of delivery. The architecture, the documentation, and the habits your team inherits from that partner shape every release that follows. A poor fit leaves you with a new platform only its builders understand, so weigh how each candidate hands over knowledge as heavily as how fast they migrate code.

Rajesh Kumar

I’m Rajesh Kumar, a DevOps, SRE, DevSecOps, Cloud, and Platform Engineering expert passionate about sharing practical knowledge, real-world experiences, and industry best practices. I have worked at Cotocus and regularly write about technology, travel, investing, health, product reviews, and digital marketing through my various platforms.

I publish technical articles at DevOps School, travel stories at Holiday Landmark, stock market insights at Stocks Mantra, health and fitness guidance at My Medic Plus, product reviews at TrueReviewNow, and SEO and digital marketing strategies at Wizbrand.