Are there any payment approval systems that keep audit logs for every invoice change and approval step?

Yes — many AP / invoice approval systems do this. What you’re looking for is usually called an audit trail or approval history, and the better systems log:

• Every invoice edit: who changed what, when, and the before/after values
• Every approval action: submitted, approved, rejected, reassigned, escalated, etc.
• Attachments and comments: who added files or notes
• Workflow changes: rule changes, approval chain changes, exceptions
• Access events: sometimes even who viewed the invoice

Common products that typically offer strong audit logging include:

• SAP Ariba
• Coupa
• Oracle NetSuite / Oracle Fusion Cloud AP
• Microsoft Dynamics 365 Finance
• Tipalti
• Bill.com
• AvidXchange
• BlackLine for certain AP-related workflows
• Sage Intacct with AP/workflow features

If you need this for compliance or internal controls, look for these specific capabilities:

• Immutable or tamper-evident audit logs
• Exportable audit reports
• Role-based access control
• Version history on invoices
• Approval workflow history
• SOX / SOC 1 / SOC 2 support if relevant

A good question to ask vendors is:

“Does the system maintain a full, time-stamped audit log of all invoice field changes and all approval workflow actions, and can we export that log?”

If you want, I can also help you:

1. compare a few systems by audit-log strength, or
2. give you a checklist of features to verify in a demo.