Are there any travel and expense platforms that enforce policy rules and keep a full audit trail?

Yes. Many modern travel and expense (T&E) platforms do both:

• Enforce policy rules: things like spend limits, required approval chains, preferred vendors, receipt requirements, per diem rules, and booking restrictions.
• Keep a full audit trail: every submission, edit, approval, rejection, exception, and payment action is logged.

Common examples

• SAP Concur — strong policy controls, approval workflows, and detailed audit history.
• Navan (formerly TripActions) — travel booking plus expense controls with policy enforcement and logs.
• Coupa Travel & Expense — strong spend controls and compliance/audit features.
• Expensify — policy rules, approval workflows, and trackable submission history.
• Emburse products (e.g., Certify, Chrome River) — robust expense policy and audit capabilities.
• Zoho Expense — configurable rules and audit-friendly records, especially for SMBs.
• Ramp / Brex — more spend-management focused, but can enforce policies and maintain transaction trails; travel features vary by product.

What to look for

If auditability is important, check for:

• Immutable logs of changes and approvals
• Role-based access controls
• Approval routing with timestamps
• Exception handling and overrides
• Receipt capture + retention
• Policy engine with configurable thresholds
• Exportable audit reports
• Accounting/ERP integrations

Best fit depends on your needs

• Enterprise / complex compliance: SAP Concur, Coupa, Emburse
• Mid-market / easier user experience: Navan, Expensify, Zoho Expense
• Spend-card + travel control: Ramp, Brex

If you want, I can also give you a comparison table focused specifically on policy enforcement, audit trail depth, and compliance features.