Migration completion gets mistaken for migration success, and the difference surfaces in the weeks after go-live: resource assignments that do not reconcile, reports that disagree with the old numbers, portfolio views that quietly drift from reality. The cause is rarely the migration itself, but the absence of structured validation after the cutover, the phase most teams skip because the data appeared to load fine.
A disciplined post-cutover audit catches those defects while they are small, before they shape a quarter of decisions made on numbers nobody checked. The checks that matter most are not evenly spaced; they cluster in the first week, tighten through the first month, and formalize by day 90.
Why the first 90 days decide migration success
The first 90 days matter because migration defects do not announce themselves. Data loads successfully and the system goes live, yet within days integration errors, reconciliation gaps, and reporting mismatches begin to surface in live processes. Research compiled by ​the Bloor Group found that more than 80% of data migration projects run over time or over budget, with cost overruns averaging 30% and time overruns averaging 41%, and much of that damage traces to validation gaps that surface after go-live.
Structured post-migration validation is what separates a controlled transition from a slow-motion problem. For PMO leaders and program sponsors, this window is not about technical confirmation. The real purpose is protecting operational continuity, financial integrity, and executive confidence in the new platform. A disciplined ​data migration approach treats validation as a defined phase, not an afterthought.
Week 1: confirm nothing critical broke
The first week is about catching the high-severity issues that disrupt daily work. Run these validations within the first days of go-live, not deferred to the following week.
Run these validations immediately:
- Reconcile record counts between the source and the new system to confirm every project, task, and resource migrated
- Verify active projects open correctly with schedules, dependencies, and assignments intact
- Confirm user access and permissions match intended roles, with no excessive or missing authorizations
- Test that critical integrations, ERP, financial, and reporting connections are passing data correctly
- Check that in-flight approvals and workflows resumed in the new environment
Integration errors often surface days after go-live, so early monitoring reduces exposure. Any critical defect found this week should be logged centrally, assigned an owner, and tracked to resolution rather than left to resolve itself. Connecting the new platform through disciplined ​business process automation helps confirm that automated workflows fire correctly.
Weeks 2 to 4: validate data accuracy and reporting
With the system stable, the focus shifts to confirming that the data is not just present but correct, and that it behaves properly inside live processes.
Reconcile financials and resource allocations
Confirm that project budgets, cost data, and resource allocations in the new system match the validated source figures. Multi-project consolidations should balance, and portfolio rollups should reconcile to the sum of their parts. Connecting this validation to trustworthy ​analytics and reporting ensures leadership sees numbers they can rely on.
Verify reports match the old baseline
Run the key portfolio and status reports in the new system and compare them against the reports the old platform produced for the same period. Discrepancies here erode executive trust fast, so any mismatch needs a documented explanation or a fix.
Confirm complex transactions are reconstructed correctly
Automated scripts verify record counts and totals, but manual review confirms that complex items, cross-project dependencies, cost-loaded schedules, and change orders are reconstructed correctly in the new environment.
Days 30 to 90: Stabilize and formalize
The final phase moves from firefighting to establishing steady-state operations and confirming the migration delivered what it promised.
Establish a reconciliation cadence
Set daily, weekly, and monthly validation cycles with clear pass-rate targets, then automate the checks where feasible. Validation should shift from reactive scrambling to a systematic rhythm embedded in governance. Building this into the ​work and operations management routine keeps data quality from drifting after the project team moves on.
Keep the legacy system in read-only mode
Retain the old platform in read-only mode for at least 90 days to support lookups and corrections that surface during normal business cycles. Decommissioning too early removes the reference point you need when a question arises about historical data.
Document lessons learned
While the experience is fresh, record which data issues caused the most remediation, which validation checks proved most valuable, and where timeline estimates missed. Capturing this improves the next migration and strengthens the ​enterprise architecture approach for future platform changes.
Close out hypercare with a formal sign-off
End the intensive support period with a documented review confirming that data is validated, reports reconcile, integrations are stable, and users are operating confidently. Formal sign-off marks the real finish line, not the cutover weekend.
Treat go-live as the start, not the finish
A PPM migration is not complete when the data loads. Completion comes when you have proven, through structured validation across the first 90 days, that the new platform holds accurate data, produces trustworthy reports, and supports the decisions your organization makes every day. The teams that treat the post-cutover window with discipline protect their credibility and their data. The ones that declare victory at go-live spend the next quarter discovering what they missed.
If your organization is planning a PPM migration or wants to validate one already underway, ​connect with Advaiya’s team. As a OnePlan managed partner with deep migration and Microsoft expertise, Advaiya helps organizations execute structured migrations and post-cutover validation that turn go-live into a controlled, confident transition.
Frequently asked questions
A post-cutover audit is structured validation performed after a project portfolio management system goes live, confirming that migrated data is complete, accurate, and behaves correctly in live processes. The audit covers record reconciliation, financial and resource validation, report verification, and integration testing across the first 90 days.
Migration defects rarely appear immediately. Within days and weeks, reconciliation gaps, reporting mismatches, and integration errors surface in live processes. Structured validation across the first 90 days catches these issues while they are small, protecting operational continuity and executive confidence in the new system.
The first week focuses on high-severity issues: reconciling record counts, verifying active projects open correctly, confirming user access and permissions, testing critical integrations, and checking that in-flight approvals resumed. Any critical defect should be logged, assigned an owner, and tracked to resolution.
Keep the legacy system in read-only mode for at least 90 days after cutover, which supports lookups and corrections that surface during normal business cycles and preserves a reference point for questions about historical data before decommissioning.
Combine automated and manual checks. Automated scripts verify record counts, sum totals, and referential integrity. Manual reviews confirm that complex transactions like cross-project dependencies and cost-loaded schedules were reconstructed correctly, and that reports match the baseline the old system produced.
Hypercare is the intensive support period immediately after go-live, typically lasting several weeks. During hypercare, the team provides rapid response to issues, monitors performance, and validates data, closing with a formal sign-off confirming the migration delivered accurate data, reliable reports, and stable integrations.
