By Hugh O. Stewart 

Accounting data migration is often described as one of the riskiest parts of an ERP transition. You’ll hear warnings about corrupted data, mismatched reports, and go-live delays from most Sage Intacct VARs and implementation guides. 

Because of this, many teams are told to ‘start fresh’ in their new system. That may work for some companies — but for many, it’s not an option. 

The traditional ETL approach is risky — but that doesn’t mean migrating historical data is irresponsible. 

We’ve completed more than 2,800 successful historical data migrations to Sage Intacct, and what we’ve discovered is that most data migration challenges are actually caused by the industry-standard ETL process used to move it.  

Below, we break down eight of the most common accounting data migration challenges and explain how our transparent, validation-driven data migration methodology can prevent them entirely.

1. Completing the Migration on Time With Limited Resources

Migrating historical accounting data isn’t like transferring data from an old iPhone to a new one. The data must be extracted, combined, deduplicated, reformatted, and enhanced with hierarchical structures, all at a mind-boggling scale. It’s not unusual for a historical migration to involve more than 1 million lines of data. To work with data at that scale, you need to have meticulous systems in place to make sure no data gets lost or corrupted.  

For a lean accounting team, trying to migrate years of historical transactions while also keeping up with daily financial operations is simply not feasible — especially not when you’re still learning your way around the new system.  

Our approach at Platform Transition reduces the customer workload by an estimated 80% by using a 10-step accounting data migration process that delivers a near-perfect migration on the first try. Our team has performed thousands of migrations across more than 80 legacy systems — so we already know the quirks, edge cases, and pitfalls that could derail your timeline. 

And because we operate on a flat fee, we’re incentivized to work efficiently and accurately to support your go-live deadline. 

2. Maintaining Confidence in Your Data Throughout the Migration

Confidence is one of the most underrated elements of a successful data migration. When finance leaders can see what’s happening, understand each step, and verify the accuracy of the work, they gain trust in the data going into the new ERP, which is one of the success factors for ERP transitions. 

But most traditional ETL processes don’t offer that clarity, because they tend to operate like a black box. They extract your data, modify it to fit import templates, load it, and then deal with the inevitable errors this process creates — often while billing hourly — until you’re satisfied with the results. All the while, you have no way of knowing whether the errors you’re seeing are caused by corruptions in your legacy data, migration mistakes, or configuration errors in the target system. 

Our process is designed to provide complete confidence in the stability of the migration at every step. We start by establishing a validation standard — a system-generated legacy report such as an AP Aging Detail Report — that we all agree accurately represents your data. From there, every step of our process is anchored to that standard. 

Using this same report, we perform five separate validation checks throughout the migration. At each checkpoint, we confirm the extracted data matches the legacy report and that nothing was lost or duplicated during the previous step.  

This level of visibility allows customers to see that their data is intact, accurate, and complete at every stage — not just at the end. By the time you reach go-live, you’ll already know the migration is right, because you will have been involved in validating the data and supporting its accuracy to that point. 

3. Uncovering Hidden Issues in Legacy Data

Most teams assume the reports their legacy accounting system produces are accurate. However, our experience has proven that this is not a safe assumption. There are dozens of errors that can cause inconsistencies between the summary data and transaction data in legacy accounting systems.  

If these inconsistencies aren’t caught at the beginning of the process, they can cause a migration to fail completely.  

Once again, our validation standard solves this problem. When we compare the raw extracted transaction data to the report the customer has agreed to use as a validation standard, we frequently discover data quality issues our customers didn’t know about.  

By exposing these discrepancies early, we help customers resolve them before they enter Sage Intacct — improving data quality at the source. This is one of the overlooked advantages of a historical migration: it not only moves your financial data, it has the potential to strengthen it, and thus strengthen your entire financial position. 

4. Avoiding the Creation of Duplicate Transactions

Duplicate transactions are one of the most damaging — and most common — risks in historical data migration. Even a single duplicated entry can distort financial statements, break reconciliations, erode trust in Sage Intacct, and force your team to spend hours cleaning up errors after go-live. 

Subledger migrations are especially prone to introducing duplicates, if they aren’t handled properly. However, bringing over your subledger detail is extremely valuable because it allows you to take advantage of Sage Intacct’s full reporting capabilities and retire your legacy system with total confidence. 

This is a common challenge in construction accounting migrations, because many legacy systems store job-cost detail (cost codes, cost types, committed costs, work-in-progress detail, etc.) outside the general ledger (GL). While the balances are reflected in the GL, the transaction-level detail is not. If you migrate both the GL and the job-cost detail independently, the financial impact of the transactions stored in the Job Cost Module will be duplicated.  

To deal with scenarios like this, we’ve developed a process called The Dimensional Enrichment Protocol^™ utilizing a series of zero-value journal entries. Instead of importing job-cost detail as standalone transactions — which would create financial duplicates — we attach the job-cost context to the corresponding GL activity using zero-value journal entries taking advantage of the dimensional reporting capabilities of Sage Intacct.  

And as always, our validation standard approach underscores each aspect of this process. If even one transaction appears twice, or appears where it shouldn’t, the numbers will immediately diverge from the validation report. This makes duplicates almost impossible to miss. 

5. Preventing Pollution from Third-Party Integrations

When third-party software integrations such as billing or payroll or expense management systems sync new transactions, they can cause the migration to appear to be unsuccessful if they’re not properly managed. Let’s take the example of Bill.com. If it pushes new invoices into Sage Intacct while we’re migrating historical invoices, when we go to check our work against the Trial Balance Report from the legacy system, the numbers won’t match, because the report compiled in Sage Intacct will include the new invoices from Bill.com usually placed in a journal not slated for migration purposes.  

As long as we know about the integrations in advance, we can factor those in when we do our checks. So to mitigate this, we take a thorough inventory of all our customer’s integrations and either pause their syncs, if feasible, or plan our validations around them.  

6. Preventing Duplicate or Inconsistent Master Data

Legacy systems often contain duplicate or inconsistent records, such as the following Vendor names: 

• “Acme Construction” 
• “The ACME Construction Co.” 
• “Acme Construction, Co” 

If you export and load these into Sage Intacct, you can end up with multiple vendor IDs assigned to the same vendor. These problems compound when you merge multiple QuickBooks files and spreadsheets. 

You can’t reliably catch these inconsistencies just by reviewing your extracted master data manually. Something as simple as the word “the” at the beginning of a company name can separate that vendor from its counterpart by thousands of lines in an alphabetical sort.  

Instead of relying on a sharp eye or memory to catch duplicates like this, we developed a proprietary process called The Duplicate Suppression System^™ that scans extracted data for master-record variations and intelligently consolidates them. 

In addition, we also provide strict guidelines to our customers to make sure they don’t create new records in Sage Intacct that could end up getting duplicated when we load the legacy data.  

7. Avoiding Errors Caused by Improper Target System Configuration

A large percentage of failed or delayed migrations can be traced back to one root cause: the target Sage Intacct environment wasn’t properly configured to receive the legacy data. 

This happens more often than people realize. Traditional data mapping typically starts late in the implementation and focuses on active master lists rather than the full set of historical transactions. As a result, essential structural elements are missing or incomplete in the target system when the migration reaches the load stage. 

This creates a number of problems:  

• Projects or customers referenced in your legacy transactions may not exist in Sage Intacct  
• Cost codes and cost types may not be configured before job-cost detail is imported  
• Vendors or customers may be created at the wrong level  

These issues lead to import errors, broken hierarchies, duplicates, inconsistent reporting, and time-consuming cleanup after go-live. 

All of this stems from one flawed assumption in the traditional ETL process: that you can design an effective Sage Intacct architecture based on industry norms and the instincts of the accounting team alone. But time and again, we find that when our customers see their data mapped out with all the hierarchical structures present in their legacy system, they realize their go-forward architecture will need to be changed — sometimes dramatically.  

We prevent these problems by building our data maps from the transactional data itself — not the active master lists. By mapping directly from the source transactions, we ensure that: 

• Every master data element — customer, vendor, project, employee, etc. — referenced in your legacy system is accounted for 
• All necessary hierarchical relationships exist in Sage Intacct before any data is loaded 
• Master data is created at the correct level, preventing duplicates and reporting inconsistencies 
• Quasi-master data (such as project cost codes and types) is set up with the proper structure 
• The configuration of the target system is fully prepared to accept the historical data without last-minute surprises 

This approach prevents the configuration errors that destabilize most migrations and ensures your data behaves exactly as expected once it reaches Sage Intacct. 

8. Minimizing Operational Downtime Without Compromising Data Quality

Downtime during an ERP transition is one of the biggest concerns for accounting teams. No one wants bills piling up, invoices going out late, or month-end work falling behind. Understandably, many teams try to keep things moving as much as possible in both systems, even while their migration is in progress. In an effort to keep up, they might: 

• Post late transactions into the legacy system after the extraction has occurred 
• Make backdated entries in Sage Intacct to clear small issues 
• Adjust prior-period activity to avoid delays in daily operations 

These actions cause problems during migration because they can violate our shared validation standard — AND, any transactions entered into the legacy system after our extraction step will never get migrated to Sage Intacct. Such well-intentioned activity during the migration period can lead to loss of confidence in the migration even though the data was extracted, converted, and loaded perfectly.  

To prevent errors like this, some data migration experts recommend a severe blackout window, where accounting teams aren’t allowed to do anything in either system — sometimes for as long as two weeks. Other teams will take the opposite approach, and try to pull off a cutover migration with no downtime. But this is a stressful, and honestly, reckless move. Even with the best of planning, the final data load can still trigger errors. If you’re under an extreme time crunch to fix those errors, you’ll likely have to take shortcuts that might destabilize the data even further. In the end, you may have to take more downtime than you would have had with a more cautious approach.  

We take a more balanced approach. We don’t ask accounting teams to sit on their hands for two weeks, but we provide clear education, expectations, and a practical work plan so everyone understands: 

• Which activities are safe during the migration window 
• Which activities must pause temporarily to protect the migration 
• How to stay productive without modifying historical data 
• How to avoid actions that would break the validation standard 

This guidance keeps the migration stable, maintains confidence in the data, and minimizes operational disruption. 

Overcome the Challenges of Migrating Historical Accounting Data with Platform Transition’s Proven Process 

The accounting industry talks about data migration as if it’s inherently dangerous, but it doesn’t have to be. 

When you replace guesswork with validation, and when you surface issues early instead of reacting to them late, historical migration can be one of the most valuable parts of a Sage Intacct implementation. It strengthens the quality of your financial data, gives you the information you need to plan a go-forward architecture that actually fits your business, and accelerates user adoption by giving your team complete confidence in the numbers from day one. 

At Platform Transition, we’ve spent years refining a 10-step methodology that eliminates the uncertainty and limitations of the industry’s standard ETL approach. The result is a transparent, repeatable process that produces clean, complete, reliable historical data — without the chaos most teams are warned about. 

If you’re preparing for a Sage Intacct implementation and want a migration process designed to avoid these challenges entirely, we’d be happy to help.  

You can Request a Quote or Schedule a Strategic Exploration Call to see what a safer, more predictable migration can look like.