ERP Migration? How to Protect Your Accounts Payable Process Before, During & After

ERP migrations (or upgrades) rarely stay in their lane. What starts as an IT-led project can quickly throw your AP process into disarray — especially if the team isn’t brought in early. Data mismatches, vendor confusion, broken workflows, delayed payments… we’ve seen it all.

In this guide, we break down exactly what to watch for before, during, and after migration — and how to keep your accounts payable operation running smoothly, no matter what’s changing behind the scenes.

Want the full discussion? Watch our expert-led webinar on preparing AP for ERP transitions.

TL;DR: What You’ll Get from This Guide

• Why ERP changes put AP processes at serious risk
• The 3 critical phases of AP migration readiness
• Tips from real-world ERP transitions (including Oracle, SAP, Microsoft Dynamics)
• A post-go-live checklist no AP lead should skip
• When to bring in your AP automation partner — and what to ask

Why ERP Migration Can Derail Your AP Workflow

Let’s be honest — AP is often left out of ERP planning conversations. Finance leadership assumes AP will “just keep working,” or worse, they don’t realize the impact until after the switch is made.

Here’s what usually breaks:

• GL structure changes that throw off invoice coding logic
• Vendor master data remapping that leads to duplicate or unmatchable entries
• Broken 3-way matching because PO and GRN logic isn’t migrated cleanly
• Lost invoice history if the cutover skips legacy data
• Automation gaps because the old system was tightly integrated with your existing AP tool — and the new one isn’t (yet)

These are real issues, not hypotheticals. We’ve seen them play out in businesses ranging from high-growth retailers to global manufacturers mid-ERP consolidation.

The 3 Phases of AP Migration Readiness

1. Before You Migrate: Clean House and Get Loud

This is your window to prepare — before code freezes and integration sprints swallow up the project.

Here’s what to do:

• Audit your current AP process: What’s working, what’s duct-taped together, and what absolutely must survive the migration?
• Map your data dependencies: GL codes, vendor hierarchies, PO structures — know what needs to be carried forward or restructured.
• Archive and analyze invoice volume: Reduce the noise. Clean out dormant vendors and stale POs that don’t need to move with you.
• Push for a seat at the migration table: If AP isn’t looped into integration planning early, you’re setting yourself up for reactive firefighting later.

Bonus Tip: Connect with your AP automation provider early — especially if your ERP platform is changing brands. Many providers (us included) maintain pre-built integrations, migration runbooks, and historical mapping tools.

2. During Migration: Test Like Your Go-Live Depends On It (Because It Does)

If you remember one thing: test everything — then test it again.

Here’s where we’ve seen transitions go sideways:

• Unvalidated vendor mapping: You flip the switch, and suddenly half your suppliers are unmatchable.
• Open POs in limbo: Invoices arrive for old POs, but your new ERP doesn’t know they exist.
• “In flight” invoices break: Anything mid-process when the cutover happens can get orphaned — and forgotten.

Your playbook should include:

• Multiple dress rehearsals of cutover with realistic test data
• Step-by-step run sheets for integration timing, data loads, and approvals
• Plans for invoice intake freeze windows (and how to handle urgent ones during downtime)
• A designated hypercare team — ideally including your AP automation partner

Don’t skip this phase. The pressure to hit ERP go-live deadlines is intense, especially near year-end. But pushing ahead without full testing is how “we’ll fix it post-go-live” turns into weeks of chaos.

3. Post-Migration: Validate, Watch KPIs, and Re-Automate

Go-live isn’t the end. It’s the beginning of your next normal — and that first month matters more than you think.

Checklist for your first 30–60 days:

1. Ensure all open POs and historical invoice data transferred correctly
2. Check automated flows tied to GLs or cost centers still work
3. Rebuild or recalibrate smart routing and approval rules
4. Monitor throughput and touchless processing rates for drop-offs
5. Watch for bottlenecks — especially if your ERP has quirks (e.g. locking POs after GRN)

When to Loop in Your AP Automation Provider (Hint: Now)

If you already use an AP automation solution, your provider should be part of your migration squad. Not an afterthought.

At SoftCo, we’ve supported ERP migrations across SAP, Oracle, Microsoft Dynamics, Infor, and beyond. Whether it’s a big-bang switch or phased rollout, we bring battle-tested checklists and hands-on consultants who’ve done this hundreds of times.

From vendor remapping to workflow migration, data cleansing to cutover support — we make sure your AP process doesn’t skip a beat. And yes, we provide post-go-live hypercare too.

Let’s Talk: Get Your ERP Migration Checklist

Already using AP automation? Planning a migration in the next 6–18 months?

We offer tailored consultations for finance and AP teams to help you:

• Identify gaps in your current process
• Map your AP workflows to your future ERP
• Build a pre/post-migration checklist
• Understand your integration options

Get in touch with our AP transition team here.