Auditing a freight invoice means reconciling it to three sources before you pay: (1) the contracted rate, (2) operational evidence of the trip (POD, appointments, logs), and (3) tax requirements (CFDI with Carta Porte 3.1). In Mexican operations at 300+ shipments per month, that reconciliation finds 2 to 7% of spend in improper charges.
Operating guide for Finance and operations: six steps, checklist, and when to move from Excel to agents. This playbook is not a tax opinion.
- pre-pay method
- 6 steps
- typical leakage found
- 2–7%
- when auditing 100%
- 5–7%
- measurable pilot
- 6–8 wks
Cluster: in-house vs software vs BPO · detention · free days · Audit Agent.
Step 1: Reconcile to the contracted rate
Compare billed base freight to the live tariff. Typical leaks: seasonal rate out of season; spot reassignment when a contract rate existed; fuel indexed with a different formula. Corridor references: Mexico City–Nuevo Laredo, Monterrey–Nuevo Laredo, Bajío–Nuevo Laredo, Manzanillo–Mexico City.
Step 2: Verify the trip happened
Cross the invoice to operational evidence: signed POD (or digital proof of delivery), confirmed appointment, GPS route when available. Freight without POD is not auditable; a fake trip or a full cancellation billed without positioning evidence is not either.
Step 3: Break accessorials apart
Every extra line (handling, reconsignment, layover, escort) must be contracted and evidenced. Uncontracted lines are clarified before pay. Size exposure with the accessorials calculator.
| Accessorial | Minimum evidence | If missing |
|---|---|---|
| Handling | Authorization + POD | Hold the line |
| Reconsignment | Written instruction | Recalculate the leg |
| Layover | Agreement + log | Do not release overnight |
| Escort | Order + time window | Validate contracted rate |
Step 4: Audit detention and clocks
Every detention charge needs arrival time, release time, and free time applied. Without a log there is no detention - only an estimate. Detail: what detention is. In ocean import, separate demurrage and storage: free days at port and terminal.
Step 5: Validate CFDI and Carta Porte 3.1
Freight with a broken Carta Porte is a double problem: tax form and deductibility. Check correct issuer (income vs transfer), SAT keys (key finder), vehicle config, and SICT permit. References: Carta Porte 3.1 guide and is freight deductible without Carta Porte?. OCL can stamp invoice and Carta Porte when the flow requires it.
Step 6: Clarify before paying
Pre-pay clarification recovers; post-pay claims beg. Log every difference, cause, and resolution - that history is your annual negotiation lever.
Method
Six pre-pay steps
Rate
Cross tariff
Trip
POD · appointment · GPS
Extras
Accessorials
Clock
Detention · demurrage
Tax
CFDI · Carta Porte
Decide
Release or hold
Select a step to see detail
Step detail · 01
Rate
Contract vs invoice
Manual, software, or BPO?
Under 100 invoices per month, a disciplined Excel checklist can work (with limits: OCL vs Excel for audit). Above 300 shipments per month, volume needs automation or outsourcing.
| Path | Coverage | Best when… |
|---|---|---|
| In-house / Excel | Sampling or hours ceiling | Low volume and complete files |
| Software / agents | 100% of pilot flow | 300+ shipments, sampling today |
| BPO | Sampling or batch | Temporary spike or backlog |
Full matrix in freight audit: in-house vs software vs BPO.
What OCL runs in the six steps
OCL Cargo is an autonomous TMS with agents and computer use (operating screens and portals like an analyst). The Audit Agent runs the six steps per shipment before pay, without replacing the tools you already run. OCL can stamp invoice and Carta Porte. Your team decides exceptions already diagnosed.
Pattern when auditing 100%: recover 5–7% of spend. Commercial reference: ~$50 MXN per shipment. Start with the free diagnostic on your latest invoices.
6–8 week pilot
One corridor, one front (pre-pay audit), frozen metrics. Do not migrate the TMS on day one.
Elige un paso para ver el detalle
Detalle del paso · 01
Set the audit universe
Key takeaways5 points
- Audit = reconcile invoice vs contracted rate + trip evidence + tax requirements, before paying.
- In Mexico, leaving sampling typically recovers 2–7% of spend (5–7% on accessorial-heavy flows).
- Six steps: rate, trip, and accessorials to detention/clocks, CFDI/Carta Porte, and documented clarification.
- Without POD or a detention log, hold: you are not “blocking the carrier,” you are not paying an estimate.
- OCL runs 100% of the pilot flow with agents; can stamp; coexistence without day-one migration; 6–8 week pilot.
How much leaks in your last 100 invoices?
Related reading
Frequently asked questions
Typically 2–7% of spend by flow: 2–4% for importers and retail, 3–5% in cold chain, 5–7% when leaving sampling in forwarder-heavy or accessorial-heavy ops. Published case: $3.6M MXN (5.7%) in 6 weeks.
It should not. Automated reconciliation takes minutes per invoice; clean invoices release faster because nobody holds them “just in case.”
Yes - recovery is often possible up to ~12 months back with a file, but yield drops over time. Pre-pay audit is the standard.
Contracted rate, operational evidence of the trip (POD, appointments, GPS), and tax requirements (CFDI with Carta Porte 3.1 when required). Without those three sources, payment is blind.
Under 100 invoices/month, a disciplined checklist can work. Above 300 shipments/month, volume needs automation or outsourcing. Compare: in-house vs software vs BPO.
Yes. The Audit Agent reconciles rate, trip, accessorials, detention, CFDI/Carta Porte and leaves documented clarification before pay. OCL can stamp invoice and Carta Porte. 6–8 week pilot without migrating the TMS on day one.