Legacy ERP Migration Timelines Are Slipping — Here's the Real Reason
It isn't the software. Undocumented custom code built up over decades is the single biggest driver of delay.
Legacy ERP migrations are slipping. Programmes planned for two years are stretching to three or four, and budgets are following. Technology leaders point to many causes, but one stands out: the hidden complexity of years of customisation that nobody fully understands any more.
The customisation iceberg
Older ERP systems were heavily tailored over decades. Each modification solved a real business problem at the time. Many were never documented, and the people who built them have long since moved on. Migration teams discover them one by one, usually during testing.
“We thought we had four hundred custom objects. We found more than two thousand.”
Other common causes
- Data quality problems that only surface during migration rehearsals
- Business teams unable to release experts for design and testing
- Integration with surrounding systems more complex than mapped
- Scope creep as stakeholders add requirements mid-programme
What successful programmes do differently
The migrations that stay closer to schedule tend to invest heavily before they start. They run automated analysis of the existing system to find customisations early, clean data months in advance, and make a firm decision to adopt standard processes unless there is a compelling reason not to.
Plan for reality
Some delay may be unavoidable, but surprises are not. CIOs who build contingency into plans, report risks honestly and secure dedicated business resources are finding their programmes far more predictable — even when they are not faster.