You're finally upgrading to a modern ERP system. The demos looked great, the sales team said all the right things, and you're ready to leave your outdated software behind. But a few months after go-live, someone on your team asks a simple question: "Can you pull up what we sold this customer two years ago?"
And suddenly, you realize nobody can.
This is one of the most common (and most preventable) problems in ERP implementations. Historical data migration tends to fall off the radar until it's too late, and by then, your options are limited and expensive. At Stellar One, we've seen this situation play out dozens of times with businesses coming from QuickBooks, legacy ERP systems, and everything in between.
In this article, we'll walk through the six most common problems that cause historical data to get lost, mishandled, or left behind during an ERP transition:
- Historical Data Gets Cut From the ERP Implementation Scope to Save Time or Money
- Legacy Systems Become Inaccessible After ERP Go-Live
- Data Quality Issues Derail the Historical Data Migration
- Imported Historical Data Distorts Current Operations in Your ERP System
- No One Maps Legacy Codes to New Codes in the New ERP Platform
- Historical Data Ends up in Spreadsheets That Nobody Can Use
By the end, you’ll fully understand what these problems are, why they occur, and what you can do to avoid each one.
1. Historical Data Gets Cut From the ERP Implementation Scope to Save Time or Money
Data migration is one of the most underestimated parts of any ERP project. When timelines slip or budgets tighten, historical data is often the first thing to go.
The logic seems reasonable at the time: "We can always go back and get it later" or "We'll just keep the old system running for lookups." But “later” rarely comes, and keeping legacy systems running creates its own problems.
How to Avoid It
Treat historical data migration as a core requirement from the start, not an optional add-on. Get a clear answer during the sales process about what's included, what costs extra, and what the timeline looks like. If your ERP partner treats it as an afterthought, that's a red flag.
2. Legacy Systems Become Inaccessible After ERP Go-Live
The backup plan for many ERP implementations is simple: Keep the old system available for historical lookups. But this approach has a short shelf life.
Hardware fails. Software licenses expire. The one person who knew how to run reports in the old system leaves the company. Within a year or two, that "accessible" legacy system becomes a black box that nobody can open.
How to Avoid It
Don't rely on your legacy system as a long-term archive. If historical data matters to your business, and it usually does, it needs to live in your new system where your current team can access it without specialized knowledge or outdated tools.
3. Data Quality Issues Derail the Historical Data Migration
Legacy systems accumulate inconsistencies over time. You might have the same customer entered three different ways, addresses formatted inconsistently, or item codes that changed halfway through your company's history.
When it's time to migrate, these issues surface fast. Some ERP partners use data quality as a reason to avoid migrating history altogether: "Your data is too messy, it's not worth bringing over."
How to Avoid It
Data cleaning is a normal part of any migration, and it shouldn't be a dealbreaker. Work with an ERP partner who has a process for staging, cleaning, and mapping legacy data rather than one who throws up their hands at the first inconsistency.
That said, perfection isn't the goal. Historical records don't need to meet the same validation standards as your live data. If an old invoice has a slightly different address format, that's fine. You're preserving a record, not mailing a letter. Focus cleanup efforts on the fields that matter for reporting: customer codes, item codes, quantities, and prices.
4. Imported Historical Data Distorts Current Operations in Your ERP System
This issue is the technical reason many ERP partners avoid historical data migration entirely and focus only on opening balance migration. If you import a three-year-old invoice directly into your new system's live tables, it can trigger unintended consequences.
The system might try to reserve inventory for a sale that was already shipped years ago. It might post to your general ledger as if the transaction happened today. Suddenly, your current inventory counts are wrong, and your financials don't make sense.
How to Avoid It
The solution isn't to skip historical data, but to store it correctly. Your ERP partner should have a way to keep historical records accessible for reporting and lookups without mixing them into your live operational data. This setup typically means separate tables designed specifically for historical documents, where they can be queried and reported on without impacting inventory, accounting, or system performance.
Ask your ERP partner directly: "If we import historical invoices, will they affect our current inventory levels or general ledger?" If they can't give you a clear answer, that's a problem.
5. No One Maps Legacy Codes to New Codes in the New ERP Platform
When you switch ERP systems, you often renumber things. Customers get new account codes. Inventory items get new SKUs. Vendors get new identifiers.
If your historical data doesn't account for these changes, you’ll lose the ability to track trends across the transition. You can't easily answer questions like "How much of this product did we sell over the past five years?" because the old records use a code your new system doesn't recognize.
How to Avoid It
Make sure your migration includes a way to store and map legacy codes. Each historical record should retain its original identifiers while also linking to the corresponding codes in your new system. This configuration will allow you to run reports that span both pre- and post-migration data without manual reconciliation.
6. Historical Data Ends up in Spreadsheets That Nobody Can Use
When proper migration isn't an option, the fallback is usually a massive Excel export. "Here's all your old data, saved to a spreadsheet."
This workaround might sound reasonable until you need to actually use it. There's no way to query it efficiently. Combining it with current data requires manual work every time. There's no version control, so anyone can accidentally modify or delete records. And good luck finding what you need in a 50,000-row spreadsheet!
How to Avoid It
If historical data is worth keeping, it's worth keeping in a usable format. That means inside your ERP system, accessible through the same interface your team uses every day, with the ability to run reports and queries without exporting and manually merging files.
Certainly, Microsoft Excel has a place next to many ERP solutions, but it’s not for housing years’ worth of historical data.
What to Ask Before You Sign on for an ERP Implementation
Before committing to an ERP implementation, ask these questions about historical data migration:
- Is historical data migration included, or is it an additional cost?
- How do you handle data quality issues in legacy systems?
- Will imported historical records affect live inventory or accounting?
- Can we track trends across legacy and new item codes?
- Where will historical data live, and how will my team access it?
The answers will tell you whether your ERP partner has actually solved this problem, or whether you'll be dealing with the consequences for years to come.
Your Next Steps for Quality ERP Platform Data Then and Now
Historical data migration doesn't have to be complicated, but it does require a partner who takes it seriously. Most of the problems above come from ERP partners who either don't have a solution or don't prioritize it.
Now that you understand what can go wrong, the next step is understanding what data is actually worth migrating. Read "Historical Data Migration: What Documents Should You Bring Over?" [coming soon] to learn which records matter most, and which ones you can leave behind.
At Stellar One, historical data migration is built into our implementation process free of charge. If you're evaluating ERP solutions and want to see how we handle it, we'd be happy to show you. Learn more on our solutions page, or get started with our free deployment below.
Frequently Asked Questions About Mistakes in Historical Data Migration