A systematic examination of expense reports, financial transactions, and supporting documentation to verify accuracy, confirm policy compliance, and detect irregularities before or after employee reimbursement.
Auditing in expense management is the structured review of employee spending records to confirm accuracy, detect policy violations, and identify fraud. It applies to every stage of the expense lifecycle, from pre-approval checks to post-reimbursement forensic reviews.
Organizations lose an estimated 5% of annual revenue to occupational fraud, with a median loss of $104,000 per case and schemes lasting a median 12 months before detection, according to the ACFE's 2026 Report to the Nations [1].
The three primary audit types for T&E are pre-payment audits (catch errors before money leaves), post-payment audits (sample-based reviews after reimbursement), and continuous audits (real-time transaction monitoring).
Navan flags policy exceptions and duplicate submissions automatically at the point of expense creation, shifting audit effort from manual post-hoc review to real-time prevention.
Effective auditing requires a mix of automated rule checks for high-volume, low-risk transactions and human judgment for complex, high-value exceptions that algorithms cannot easily categorize.
What is Auditing?
Auditing is the systematic process of examining financial records, transactions, and supporting documentation to verify their accuracy and compliance with established rules. In the context of business travel and expense management, auditing specifically refers to reviewing expense reports, corporate card transactions, and reimbursement claims to confirm that every dollar spent aligns with company policy and applicable regulations.
The scope of an expense audit ranges from verifying that a receipt matches a reported amount to analyzing spending patterns across an entire organization to detect anomalies. Unlike a simple approval (where a manager confirms a report looks reasonable), an audit applies structured criteria: documented thresholds, sampling methodologies, and evidence standards that make findings defensible.
Expense auditing sits at the intersection of finance, compliance, and risk management. Finance teams need accurate data for close and reporting. Compliance teams need proof that policies are followed. Risk teams need early detection of fraud or misuse before losses compound.
Why Expense Auditing Matters for Businesses
The ACFE's 2026 Report to the Nations analyzed 2,402 fraud cases across 143 countries and found that organizations lose approximately 5% of revenue to occupational fraud annually [1]. The median fraud case lasted 12 months before detection, and schemes discovered within six months caused median losses of $40,000 compared to over $1.1 million for those lasting beyond five years.
For T&E specifically, the risk concentrates in three areas:
Duplicate submissions: The same expense claimed on multiple reports or across both a corporate card statement and a manual reimbursement request.
Policy violations: Spending above approved thresholds, booking outside preferred channels, or claiming non-reimbursable categories (personal meals, upgrades without justification).
Fictitious expenses: Fabricated receipts, inflated amounts, or claims for trips and meals that never occurred.
Without structured auditing, these issues compound silently. A $200 monthly policy violation across 500 employees adds up to $1.2 million annually in undetected overspend.
Types of Expense Audits
Different audit approaches serve different purposes. Most organizations use a combination.
Audit Type
Timing
Coverage
Best For
Pre-payment
Before reimbursement
100% of flagged items
Catching errors and policy violations before money moves
Pre-payment audits prevent losses but add processing time. Post-payment audits are less disruptive but require recovery of already-disbursed funds. Continuous auditing uses automated rules to monitor every transaction in real-time, flagging only the exceptions that need human review.
How Does an Effective Audit Process Work?
A well-designed T&E audit process follows five stages:
1. Define audit criteria. Establish which rules will be tested: spending limits by category, receipt requirements above certain thresholds, travel policy compliance standards, and documentation completeness. These criteria must be specific enough to produce consistent results regardless of who performs the audit.
2. Select the audit sample. For post-payment audits, determine the sampling methodology. Common approaches include random sampling (every report has equal probability), risk-based sampling (higher-risk submitters or categories get more scrutiny), and stratified sampling (proportional coverage across departments or spend tiers).
3. Execute the review. Compare each selected transaction against the defined criteria. Check receipt presence, verify amounts match, confirm dates align with travel records, validate that approvals followed proper workflow, and test categorization accuracy.
4. Document findings. Record every exception with its severity, the rule violated, the dollar amount at stake, and whether the issue appears isolated or systemic. This documentation creates the audit trail needed for follow-up action.
5. Report and remediate. Share findings with stakeholders, recover overpayments where applicable, update policies to close gaps, and feed insights back into the expense tracking system to prevent recurrence.
The organizations that catch problems early share several characteristics in their audit approach.
Risk-based prioritization. Not every $12 coffee receipt warrants the same scrutiny as a $3,000 client dinner. Effective programs assign risk scores based on amount, category, submitter history, and timing, then concentrate human review on the highest-risk items while automating low-risk checks.
Separation of duties. The person who approves an expense should not be the person who audits it. When these roles overlap, a single point of failure exists. In smaller organizations where full separation isn't feasible, compensating controls like periodic external review fill the gap.
Clear escalation paths. Auditors need defined protocols for what happens when they find a violation. Minor issues (missing receipt, wrong category) follow one path. Suspected fraud follows another, typically involving legal and HR before confronting the submitter.
Regular policy refresh. Audit findings should feed back into policy design. If 40% of exceptions come from a single ambiguous rule, the rule needs rewriting rather than more enforcement of a confusing standard.
When Should Companies Consider External Audits?
Internal audit teams handle routine expense reviews, but external auditing becomes necessary in specific situations.
Regulatory requirements. Public companies subject to Sarbanes-Oxley (SOX) Section 404 need external verification that financial controls, including T&E controls, operate effectively. Government contractors may face additional audit requirements under FAR (Federal Acquisition Regulation) clauses.
Suspected systemic fraud. When internal indicators suggest coordinated fraudulent activity (collusion between approvers and submitters, for example), external forensic auditors bring independence and specialized investigative techniques that internal teams may lack.
M&A due diligence. Acquiring companies often audit the target's expense patterns to understand true operating costs and identify hidden liabilities or compliance risks that standard financial statements don't reveal.
Post-incident review. After a significant fraud event, external auditors assess what controls failed, how long the scheme operated undetected, and what redesigns are needed. The ACFE found that 43% of occupational fraud is detected through tips rather than controls [1], suggesting that proactive expense reconciliation and monitoring remain underdeveloped in many organizations.
Related Terms
Audit Trail: The chronological record of every action taken on a transaction, from submission through approval and payment, providing the documentary evidence that auditors examine.
Expense Fraud: The deliberate falsification or manipulation of expense claims for personal gain, which auditing is specifically designed to detect and deter.
Travel Policy Compliance: The degree to which employee booking and spending behavior adheres to established corporate travel rules, measured through audit reviews.
Internal audits are conducted by an organization's own finance or compliance team to monitor ongoing policy adherence and catch errors before they compound. External audits are performed by independent third parties, often required for regulatory compliance (SOX, FAR) or during investigations where objectivity matters. Internal audits happen continuously; external audits are periodic or event-driven.
Most organizations audit a statistical sample (10-25%) of expense reports monthly while running automated rule checks on 100% of submissions in real-time. High-risk categories like entertainment, travel upgrades, and cash advances may warrant higher sampling rates. The ACFE recommends that no category go unreviewed for more than 90 days to prevent small issues from becoming systemic problems.
Key indicators include round-dollar amounts (real expenses rarely end in .00), duplicate submissions on consecutive reports, expenses just below approval thresholds, weekend or holiday charges with no corresponding travel record, and receipts from vendors that don't match the reported location. Navan's automated audit rules flag these patterns at submission, reducing the volume requiring manual review.
Both. Pre-payment audits and real-time monitoring prevent fraud by catching violations before money moves. Post-payment audits detect fraud that bypassed initial controls. Perhaps more importantly, visible audit programs create deterrence: employees who know reports are reviewed behave differently than those who believe no one checks. The ACFE found that organizations with proactive data monitoring cut median fraud losses by more than 50%.
Automated auditing applies consistent rules to 100% of transactions instantly, catching pattern-based violations like duplicates and threshold breaches with no human effort. Manual review is better for judgment calls: whether a $500 client dinner was appropriate context, or whether a business-class upgrade was justified. Navan combines both, auto-resolving clear-cut items and routing edge cases to human auditors with relevant context attached.
Audit-ready organizations retain original receipts (digital or physical), approval chain records showing who approved and when, corporate card statements matched to expense reports, travel itineraries confirming dates and destinations, and policy acknowledgment records proving employees understood the rules. Retention periods vary: the IRS requires at least three years for most business expense records, though some industries mandate seven or more.
Accrual accounting is a method of recording financial transactions when they occur, regardless of when the cash transactions happen, ensuring that revenue and expenses are matched in the period they arise.
