Keep the systems your business depends on stable, secure and running. We provide SLA-backed support for older custom software, ERP and CRM systems: 24/7 monitoring, bug fixes, security patching, performance tuning and documentation, even if the original developers are long gone.
- 24/7 automated monitoring
- SLA-backed response times
- We take over existing systems
- Monthly reporting
What is legacy application support?
Legacy application support is the ongoing maintenance of older software your business still relies on: a custom ERP, a CRM built years ago, a customer portal or an internal tool that runs key processes. It keeps those systems reliable and secure while you decide whether, and when, to modernise them.
Good legacy software support goes beyond fixing things when they break. It means monitoring for problems before users notice, keeping servers and dependencies patched, improving performance, and documenting the system so it no longer depends on one person's knowledge.
Signs your legacy system needs support
- No one knows how it worksThe original developer has left and there's little or no documentation.
- Frequent outages or errorsUsers report crashes, slow pages or failed processes.
- Unpatched softwareServers, frameworks or libraries haven't been updated in years.
- Fixes take too longSimple changes are risky or have no one to make them.
- Integrations breakingThird-party APIs change and the system stops syncing.
- Audit or security concernsPenetration tests or insurers flag outdated components.
Our legacy support services
Application maintenance services that keep older systems dependable day to day.
Monitoring and alerting
24/7 automated monitoring of uptime, errors, performance and key processes, with alerts to our team.
Bug fixes and incident response
Prioritised fixes with agreed response times, root-cause analysis and follow-up to stop repeat issues.
Security patching
Server, framework and dependency updates where supported, plus mitigations where full patches aren't possible.
Performance tuning
Database, query and server optimisation to fix slow screens and timeouts.
Backups and recovery
Backup checks and tested restore procedures, so you can recover if something goes wrong.
Integration maintenance
Keeping connections to payment, accounting, email and other systems working as APIs change.
Documentation
Architecture, deployment and runbook documentation for systems that have none.
Knowledge transfer
Sharing what we learn with your team, so knowledge isn't locked in one person or supplier.
Small enhancements
Minor changes and reports within your monthly allowance.
Support plans and SLAs
Choose the level of cover your system needs. Every plan includes 24/7 automated monitoring, a named support contact and a monthly report.
Essential
- Business-hours support, Monday to Friday
- Critical issues: response within 4 business hours
- Monthly security updates where available
- Small allowance for fixes and changes
Standard
- Extended business-hours support
- Critical issues: response within 1 hour
- Proactive patching and performance reviews
- Larger allowance for fixes and enhancements
- Quarterly health check and roadmap review
Enterprise
- Out-of-hours cover for critical incidents
- Critical issues: response within 30 minutes, 24/7
- Uptime targets where we manage the hosting
- Dedicated support team and monthly service review
How we prioritise issues
| Priority | Example | Essential | Standard | Enterprise |
|---|---|---|---|---|
| P1 Critical | System down or major function unavailable | 4 business hours | 1 hour | 30 minutes, 24/7 |
| P2 High | Key feature impaired, workaround available | 1 business day | 4 business hours | 2 hours |
| P3 Normal | Minor bug or non-urgent issue | 3 business days | 2 business days | 1 business day |
| P4 Request | Small change or question | Scheduled | Scheduled | Scheduled |
Response times are targets for acknowledging and starting work. Uptime commitments apply where we manage hosting and are set out in your SLA. Prices exclude VAT.
Legacy support vs modernisation
Support keeps your current system running. Modernisation changes it. Many businesses need both: stabilise first, then modernise in stages.
| Legacy application support | Legacy modernisation | |
|---|---|---|
| Goal | Keep the existing system stable and secure | Upgrade, re-architect or replace the system |
| Cost model | Monthly retainer | Project-based |
| Best when | The system still meets business needs | It's out of support, costly to change or limiting growth |
| Typical outcome | Fewer outages, patched software, documentation | Supported technology, faster changes, cloud readiness |
Ready to upgrade? See our legacy app modernisation services, or move off ageing servers with our cloud migration services.
Technologies we support
| Area | Technologies |
|---|---|
| Back end | .NET Framework and .NET, older PHP versions and frameworks, Java, Node.js |
| Front end | AngularJS, jQuery, ASP.NET Web Forms and MVC, older React and Angular |
| Databases | SQL Server, MySQL, PostgreSQL, Oracle |
| CMS and ecommerce | WordPress, Drupal, Magento |
| Mobile | Xamarin, older native iOS and Android apps |
| Hosting | Windows and Linux servers, on-premise, AWS and Azure |
Not sure if we can support your system? Tell us what it runs on and we'll confirm during the audit.
Cost of legacy support in the UK
Most legacy support is a monthly retainer. What you pay depends on these factors:
System size and condition
Larger or poorly documented systems need more time to support safely.
Response times
Faster responses and out-of-hours cover cost more.
Technology
Older or less common technologies need scarcer skills.
Hosting
Whether we manage servers and backups or you do.
Change allowance
How much development time you need each month for fixes and changes.
Onboarding
A one-off audit and stabilisation phase for systems with known issues.
Typical retainers start from around £500 a month. If support costs keep rising, modernisation may be cheaper long term; see our software development cost guide.
Get a free legacy support audit
Tell us about your system. We'll review its health, risks and documentation, and recommend the right level of support.
Industries we support
Manufacturing
Production, stock and ERP systems that run the factory floor.
Logistics
Job, fleet and warehouse systems with many integrations.
Professional services
Case, client and billing systems built years ago.
Retail and ecommerce
Older stores and order systems connected to stock and accounts.
Healthcare and care
Booking and record systems that must stay available.
Education and membership
Portals, CRMs and course systems with long histories.
Our onboarding process
Audit
Review code, hosting, access, backups, security and documentation.
Handover
Secure access transferred and knowledge captured from your team or previous supplier.
Stabilise
Fix urgent risks, such as missing backups or critical vulnerabilities.
Monitor
24/7 monitoring and alerting switched on, and SLA support begins.
Improve
Ongoing fixes, patching, documentation and a modernisation roadmap if needed.
Why work with Fulminous Software
We take over existing systems
Support for software built by other teams, with a structured handover.
Clear SLAs
Agreed response times and priorities in writing.
Support and modernisation
One team that can keep your system running and plan its future.
Transparent pricing
Fixed monthly retainers in GBP, with VAT shown separately.
Monthly reporting
What we fixed, patched and found, and what we recommend next.
London-headquartered
UK business-hours support, with out-of-hours cover on higher plans.
Legacy application support FAQs
What is legacy application support?
Legacy application support is the ongoing maintenance of older software that your business still relies on. It covers monitoring, fixing bugs, applying security patches, keeping servers and dependencies stable, improving performance and documenting how the system works, so it stays reliable until you modernise or replace it.
Can you support an application someone else built?
Yes. Most of our support work starts with systems built by other teams. We begin with an audit of the code, hosting, access and documentation, then stabilise anything urgent before moving to routine support.
What response times do you offer?
Response times depend on your plan and the severity of the issue. Critical issues get the fastest response, with out-of-hours cover on our higher plans, and lower-priority requests are handled within business hours. Exact targets are set out in your SLA.
Do you provide 24/7 monitoring?
Yes. We set up automated 24/7 monitoring and alerting for availability, errors and performance. Out-of-hours human response for critical incidents is included on our higher support plans.
How much does legacy application support cost in the UK?
As a guide, essential support starts from around £500 a month, standard support with faster response times and regular maintenance typically costs £1,500 to £3,000 a month, and enterprise support with out-of-hours cover is quoted individually. The cost depends on the system's size, condition, technology and required response times.
Do you support legacy ERP and CRM systems?
Yes, including custom-built ERP and CRM systems and older integrations between them. For packaged products, we support the custom code, integrations, hosting and data around them, and work alongside the vendor where vendor support is needed.
Should we support our legacy system or modernise it?
Support makes sense when the system still meets your needs and you want it stable and secure. Modernisation makes sense when it's out of vendor support, expensive to change or holding the business back. Many businesses do both: stabilise first, then modernise in stages.
What happens if our developer has left and there's no documentation?
That's common. During onboarding we review the code, map the architecture and integrations, recover access to hosting and accounts where possible, and create documentation so the system is no longer dependent on one person.
Do we keep ownership of the code?
Yes. Your code, data and accounts stay yours. Any documentation and improvements we create during support are handed over to you.
Need reliable support for a legacy system?
Tell us what you're running and what's going wrong. We'll audit it and recommend the right support plan.
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