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Legacy ERP System Migration Explained: Step-By-Step Playbook

Written by Martus Solutions | November 02, 2025

Outgrowing your older ERP system and looking to upgrade it?

Many mission-first organizations are finding new ways to strengthen their financial and operational processes while building on the systems they already trust. 

How? Through modern tools that can migrate existing data to a cloud-based equivalent, making it easier than ever to enhance efficiency and collaboration. 

In today’s article, we will explore how you can modernize your financial management practices through a strategic integration that supports structured legacy ERP system migration.

We'll also explore the best platform that meets you where you are, without necessarily replacing what you have. 

Let’s get started. 

What is a Legacy ERP System?

A legacy ERP system is an older version of enterprise resource planning software that organizations use to manage core functions such as accounting, budgeting, and operations.

Legacy systems are typically installed on-premises, which means they run on local servers rather than in the cloud. They are also built on outdated technology and rigid architectures. 

For mission-driven organizations and small to midsize businesses, legacy ERPs create several challenges:

  • Limited financial transparency: ERP data is often kept in silos, which necessitates manual data entry or spreadsheets to consolidate reports. Financial reporting slows down, making it difficult to see the full picture of your overall financial health. 
  • Poor Scalability: Legacy ERPs don't adapt easily to growing organizations or changing needs. To add new features, users, or integrations, you would need extensive IT support or an expensive upgrade. 
  • Restricted Collaboration: Poor integration with other tools and a lack of remote access mean distributed teams struggle to share data. 

Unlike legacy systems, modern cloud-based ERP systems prioritize flexibility and ease of use. They offer automated workflows, real-time reporting, and seamless integrations. 

Modern ERP platforms give teams and leaders instant visibility into financial activities and results. They are accessible from anywhere, update automatically, and scale as your organization grows. 

With a modern ERP system, you can focus less on managing systems and more on advancing your mission. 

Signs Your Legacy ERP System Needs Replacement

If you are struggling to maintain proper nonprofit financial management, your current legacy ERP might be holding you back. 

Let's explore some common signs your legacy ERP may need replacing:

  • Slow Performance: When the system lags, or it takes you hours to make reports, it's time to change it. A nonprofit managing multiple grants or programs can be disadvantaged because these delays can stall critical funding decisions. 
  • Manual Data Entry: If you are still exporting data to spreadsheets you've outgrown or re-feeding numbers from one system to another, inefficiencies and errors are inevitable. Activities such as tracking donor funds or maintaining audit-ready records become a burden. 
  • Lack of Real-Time Visibility: Most legacy ERP tools can't display up-to-date financial data, leaving finance leaders and other staff without a clear view of budgets, forecasts, and actuals. Strategic planning or adjusting to shifting priorities becomes harder.  
  • Integration Issues: Older systems rarely connect smoothly with modern tools like Sage Intacct and QuickBooks. They also don't connect well with modern payroll and fundraising platforms. The data silos that stem from these incompatibilities limit collaboration across locations and departments. 

An outdated system delays insight and undermines mission-first decision-making. 

You'll want to treat a system upgrade as an opportunity rather than a disruption to leverage collaboration, transparency, and long-term financial stewardship. 

Steps Involved in Legacy ERP Migration

What should you do once you establish that you need to replace or migrate your legacy ERP software based on one or a combination of these signs? 

Here are the main steps to consider:

1. Assessing Your Needs

Start by identifying what your existing system lacks and what your organization needs to move forward. 

Ensure you involve finance, IT, and non-finance teams to align on goals, workflows, and reporting needs. 

Assessing your needs lays the foundation for a successful migration because you can clarify priorities, define measurable outcomes, and avoid scope creep later on. 

2. Data Mapping

Review where your current financial, personnel, and operational data lives. Liaise with all the necessary stakeholders and agree on how you'll transfer this data to the new system. 

Proper ERP data migration ensures budgets, grants, and donor records move accurately and remain audit-ready. 

Thorough data mapping will minimize errors, ensure data consistency, and help you clean or consolidate information before the transfer. 

3. Integration Planning

At this stage, evaluate how the ERP integration will happen, depending on the financial tools you use.

Determine which systems (payroll, donor management, or fund accounting) will connect to the new tool to ensure seamless data flow and compatibility.

4. Migration Testing 

Your team should test data transfers, user access, and workflows in a controlled environment before the new ERP system starts operating. 

The testing step helps you catch errors early and ensure your teams are comfortable with the new system. 

By simulating real-life use cases during testing, you can ensure that integrations, permissions, and reporting features perform as expected before the full deployment. 

5. Going Live with the New ERP

Once testing proves it can work, roll out the new platform in phases while maintaining clear communication and strong support for all team members. 

Continue validating data and collecting feedback from your staff members to fine-tune various processes after the launch. 

A phased rollout allows your teams to adopt gradually, reduces operational risks, and helps you make adjustments based on early feedback. 

If your migration is done in well-planned phases and guided by testing, collaboration, and cross-functional communication, you set yourself up for smoother operations and better financial insight. 

Common Challenges and How to Solve Them

As you follow these legacy system migration steps, remember that the whole exercise is a significant step forward and comes with unique challenges. 

Be on the lookout for the common hurdles below:

  • Risk of Data Loss: Transferring years of funder, personnel, and financial data can be daunting, resulting in the loss of critical information. To minimize risk, back up all your records, validate data during testing, and work with vendors with direct experience in nonprofit financial management systems. 
  • System Downtime: Both short and long interruptions can disrupt key activities such as payroll or grant tracking. Use a phased rollout plan and cloud integrations to keep essential functions running during the transition. 
  • Staff Resistance: Migrating to a cloud-based ERP solution can be a stressful change if your team is already stretched thin. Some staff members might prefer their familiar ERP. To minimize this effect, offer hands-on training and communicate how the new system simplifies financial processes and reduces manual work. 
  • Cost Overruns: The cost of a legacy-to-cloud migration can skyrocket when unexpected issues arise. You can control costs by setting clear milestones, monitoring progress, and choosing a scalable solution that fits your budget and capacity. 

While migrating legacy systems to the cloud is often overwhelming, the right approach and tools can make it manageable. 

With Martus, our nonprofit financial management platform, you can upgrade your finance ecosystem without heavy IT support or costly disruption. 

Here's how Martus helps:

  • Seamless ERP Legacy System Integration: Martus connects to over 20 accounting and ERP systems, so you can keep using your favorite finance technology. For example, Martus connects with legacy systems that rely on flat-file imports, such as MIP and Great Plains. 
  • Eliminates the need to Modernize Your ERP: When you work with us, you don't have to ditch your ERP or modernize it yourself. All you need to do is integrate it with our platform and automatically import data from the ERP into our platform’s financial tools. 
  • Alternative Integration Options: Martus can integrate with your ERP system using API. If your ERP doesn't support API, Martus EZ Connector provides a reliable solution. You can use it to complete file-based integrations with systems such as Aplos, Sage 50, Sage 200, Sage 300, Solomon, MIP Server, ACS Realm, and more. 
  • Centralized Control and Ease of Use: Connecting to diverse accounting and ERP systems enables seamless data flow, bringing all your financial data into a single, centralized point of truth and control. Our cloud-based platform is also easy to use, with conversational dashboards, an intuitive interface, and automatic data pulls that reduce the need for extensive training. 

Streamline your legacy ERP system integration and data migration with Martus — consult with our experts today.

Best Practices to Ensure a Smooth ERP Migration

A successful legacy system replacement strategy goes beyond flipping the switch to ensure the new tech setup truly supports your mission goals. 

We recommend various best practices to keep the process smooth and effective:

  • Set Success Metrics: Define what success will look like. Think of metrics such as improved data accuracy, higher staff adoption rates, and faster financial reporting for measuring progress and guiding decisions. 
  • Foster Cross-Department Collaboration: Involve finance, IT, and other leadership teams throughout the process, from researching legacy migration solutions to the actual data migration. Collaboration ensures the migration aligns with their needs and supports daily workflows and long-term strategic goals. 
  • Choose Cloud-Based Migration Solutions: Go for a platform that's intuitive, flexible, scalable, and transparent. A cloud system dedicated to mission-driven organizations and businesses simplifies updates, enables real-time data synchronization, and reduces IT burdens. 
  • Perform Post-Migration Reviews: After launching the newly integrated ERP, review the quality of your data, reporting efficiency, and staff feedback. Use the insights from this exercise to fine-tune your workflows and strengthen financial visibility over time. 

You'll want to combine clear goals, collaboration, and continuous improvement to ensure your ERP migration provides a firm foundation for more intelligent, more transparent financial management. 

Frequently Asked Questions (FAQs)

We'll close our discussion by answering common questions nonprofit leaders often ask about legacy ERP system migrations:

How Long Does a Typical Legacy ERP Migration Take?

The duration for a legacy ERP migration varies by organization size, data complexity, and integration needs. 

The timelines can range from several weeks to a few months.

Your organization can use a modern service provider to leverage prebuilt integrations and an intuitive interface, which can shorten migration time and minimize disruption.

How Can Businesses Ensure Data Security During ERP Migration?

During data migration for legacy systems, you can ensure data privacy through encrypted data transfers, secure backups, and the use of trusted cloud vendors with strict compliance standards.

Modern ERP-compatible systems follow best-in-class security protocols and maintain data integrity during migration.

Can We Migrate in Phases or Does It Need to Be All at Once?

Phased migrations are often safer. They allow you to test functionality before full implementation.

You can start with critical modules, such as nonprofit collaborative budgeting or reporting, to build confidence and minimize operational disruption.

Once you've achieved some success, proceed with other modules such as forecasting, personnel planning, and cash flow forecasting

How Do We Maintain Business Operations During the Migration?

We advise our clients to run legacy and new systems in parallel temporarily whenever possible to ensure continuity.

Proactive training and communication will help finance and operations teams adapt smoothly.

Additionally, choosing a cloud-based integration reduces downtime and maintains uninterrupted financial visibility.

Conclusion

Modernizing from an outdated ERP is much more than an IT upgrade. It’s a strategic step toward better transparency, efficiency, and mission alignment when it comes to managing your organization's finances. 

Since a legacy ERP system migration can be costly and confusing, it's best to adopt the right approach and platform to make the process friendlier. 

At Martus, we believe that the best innovations don't always have to replace what you have. They are about making it work better.

Our cloud-based financial management platform leverages both APIs and file-based systems to seamlessly integrate with your ERP, unifying your financial data in real time and improving accuracy.

You also get intuitive insights that empower your team to make data-driven financial decisions that align with your mission. 

See how Martus integrates with your current systems to streamline budgeting, forecasting, and reporting — schedule a personalized demo today