Your factory throws in a dozen extra phone cases as a goodwill gesture before sealing the container. The SAT doesn’t see a gift. It sees merchandise with no pedimento covering it — and that’s the legal definition of contraband.
That’s the mechanic behind two of the most common, least understood customs discrepancies importers run into: sobrantes (merchandise found in excess of what’s declared) and faltantes (merchandise short of what’s declared). Under Mexico’s Ley Aduanera, the SAT treats these two situations differently, and neither treatment is forgiving. Sobrantes trigger a presumption of contraband under Article 176, fracción X. Faltantes trigger scrutiny of your declared value and commercial data under Article 184-A, with fines that rose sharply under the reform that took effect January 1, 2026.
If your pedimento is built from a packing list your Chinese supplier put together the night before the container left the factory, you’re carrying more exposure than you think.
What Are Sobrantes and Faltantes, and Why Do They Happen So Often With Asian Suppliers?
A sobrante is merchandise physically found in your shipment that exceeds the quantity declared on your pedimento. A faltante is merchandise declared on your pedimento that isn’t physically there when the container is opened.
Both come from the same root cause: your customs paperwork is built from data your supplier provides, not from an independent count. In practice, that means:
- The factory adds “free” units — replacement stock for expected defects, samples for your next order, or simply extra pieces from an overrun — without updating the packing list.
- The factory undercounts or miscounts cartons during a rushed loading, and the shortfall isn’t caught until Mexican customs opens the container.
- A carton gets mislabeled, double-counted, or left off the manifest during a multi-SKU consolidation.
None of this is unusual on the factory floor. It’s exactly the kind of gap a container-loading check catches — and exactly the kind of gap your broker in Mexico has no way to see, because by the time the pedimento is filed, the container is already at sea.
Why Does the SAT Treat Sobrantes as Contraband?
A sobrante is contraband because the excess units have no pedimento covering them — and merchandise without a pedimento is, by definition, illegally in the country.
Article 176, fracción X of the Ley Aduanera states that an import infraction occurs when merchandise can’t be shown, through the corresponding customs documentation, to have gone through the legal process for entering the country. The law is explicit that this includes merchandise presented to the automated selection mechanism without a pedimento, or with a pedimento that doesn’t correspond to it. An extra unit found in your container during reconocimiento aduanero (the physical customs inspection) falls squarely into that category — it’s real, it’s sitting in your container, and no pedimento says it should be there.
The financial exposure is defined by two articles working together:
- Article 151, fracción IV — If the inspector detects undeclared or excess merchandise exceeding 10% of the total value declared in your customs documentation, the goods are subject to immediate embargo precautorio (precautionary seizure). This isn’t a warning letter. It’s your container being held, on the spot, during the inspection.
- Article 178, fracción IX — Once the infraction is confirmed, the fine equals the range set out in fracciones I through IV of that article: 130% to 150% of the omitted duties, or, if the goods would otherwise have been duty-exempt, 70% to 100% of their commercial value.
Run the arithmetic on a mid-sized container. If your declared commercial value is USD 50,000, the 10% embargo threshold is USD 5,000 — the value of a few dozen units on many consumer goods orders. A handful of “extra” phone cases, a spare box of eyewear samples, or an overrun of packaging inserts can clear that line without anyone at the factory thinking twice about it.
What Actually Happens When an Inspector Finds a Sobrante?
If the excess trips the 10% threshold, the customs officer opens a Procedimiento Administrativo en Materia Aduanera (PAMA) on the spot, under Article 150. You’ll receive an acta de inicio — a formal record naming the authority involved, describing what was found, and identifying the merchandise embargoed.
From there, the clock starts:
- 10 business days to submit evidence and arguments proving the excess merchandise was, in fact, legally covered — a corrected invoice, proof the goods were part of the same commercial operation, or evidence the discrepancy falls under an available exception.
- Up to 4 months for the customs authority to issue a resolution once the evidence period closes — either releasing the goods with no penalty, or confirming the infraction and applying the fine under Article 178, fracción IX.
Your container sits in the customs yard the entire time. Demurrage, storage, and idle trucking accrue regardless of how the case eventually resolves. Even a resolución absolutoria — a full win — doesn’t refund the weeks the container spent parked.
Here’s how it actually plays out on the ground: the packing list says 5,000 units. The inspector’s tally comes back at 5,140. That gap — 140 units, roughly 2.8% by count — might sit under the 10% value threshold on a low-cost SKU, or clear it easily on a higher-value one, depending entirely on what those extra units are worth. Nobody at the factory kept a record of why the count was off. Your broker in Mexico has no way to explain it, because your broker never saw the container loaded. The only person who can answer the inspector’s question in real time is standing at the factory, three weeks earlier — or nobody is.
Why Are Faltantes Treated as Misdeclaration Instead of Smuggling?
A faltante doesn’t bring undeclared goods into the country, so it doesn’t trigger the same contraband presumption a sobrante does. But it does mean the data on your pedimento is wrong — and accurate data is a standalone legal obligation, independent of whether duties were correctly paid.
Every pedimento is built on top of an Acuse de Valor (COVE), transmitted through VUCEM under Articles 36-A and 59-A, declaring the value, quantity, and commercial details of your merchandise. Article 184-A, fracción I makes it an infraction to transmit inexact or false data regarding the value of the merchandise or other data related to its commercialization — and a quantity that doesn’t match what’s physically in the container is exactly that.
The fine, under Article 184-B, applies per transmission. As of the January 2026 reform, the range for this infraction rose from $29,420–$49,050 pesos to $53,500–$106,970 pesos — more than double the previous ceiling.
The deeper risk isn’t the fine itself. A faltante means your declared per-unit value was calculated against a quantity that doesn’t exist, which puts your entire transaction value on shakier ground. If the SAT decides to question that value under Articles 72, 73, or 78-A — a determination it’s entitled to make whenever the declared value looks unreliable — you’re no longer dealing with a documentation fine. You’re dealing with a full valuation review, and if that review finds duties were underpaid as a result, the exposure escalates to the 130–150% range under Article 178, fracción I.
How Strict Is the SAT About Data Accuracy on the Pedimento?
The pedimento isn’t a summary. It’s a formal fiscal declaration, and every field on it — quantity, value, description, tariff classification, NOM compliance data — is treated as a statement of fact the importer is legally responsible for, whether or not the importer personally counted the goods.
That standard got measurably stricter under the Ley Aduanera reform published in the DOF on November 19, 2025, effective January 1, 2026. Among other changes, the reform removed the liability exclusions that previously let a customs broker distance themselves from data supplied by the importer. Before the reform, an agente aduanal could argue an error originated with the client’s paperwork and share less of the exposure. After it, brokers carry more of that risk directly — which is why more of them are pushing verified counts and values back onto importers before they’ll file, rather than taking a factory-issued packing list at face value.
Put plainly: the tolerance for “close enough” data has gone down, not up, in 2026. A 10% sobrante threshold sounds like room to breathe. On a container full of small consumer items, it’s a margin one uncounted carton can clear.
How Do You Make Sure Your Paperwork Matches What’s Actually in the Container?
The only way to guarantee your paperwork matches your physical cargo 100% is to perform an aduanal-grade inspection before the container is sealed in China — and that’s where QCADVISOR’s previo en origen comes in.
A previo en origen is a physical count and documentary review, done at the factory before the container leaves, built to the criteria your customs broker actually needs rather than a generic quality check. Our inspectors:
- Count every carton against your commercial invoice and packing list, unit by unit, before loading — not after your broker has already built the pedimento around whatever number the factory sent.
- Flag “extra” units on sight, whether they’re genuine free samples, overrun stock, or a miscount, so you decide what goes on the invoice before it’s sitting undeclared in a sealed container.
- Verify NOM labeling and other commercial-information data matches what your broker will transmit through the COVE — the same data now facing sharper Article 184-A/184-B enforcement.
- Photograph the loading process carton by carton, so the count that leaves the factory is the count your broker files.
Every inspection runs on standard field rates starting at USD 280 per man-day across most of Asia, with travel included for factories in mainland China. Our inspectors rotate between assignments and never accept factory-arranged transport, because an inspector the factory drives to lunch is an inspector the factory owns. That independence is the point — a set of eyes that works for you, not for the supplier trying to hit a shipping deadline.
What Does a Discrepancy Cost You at the Port Versus at the Factory?
A previo en origen catches a sobrante or faltante while it’s still a five-minute conversation with a factory manager. Catching the same discrepancy at Mexican customs is a different order of problem.
| Caught at the factory (previo en origen) | Caught at Mexican customs | |
|---|---|---|
| Cost to fix | Recount and correct the invoice before sailing — no cost beyond the inspection | Container embargoed; demurrage, storage, and idle trucking accrue during the case |
| Timeline | Resolved same day, before the seal goes on | 10 business days minimum for evidence, up to 4 months for resolution |
| Financial exposure | None — the pedimento is built from a verified count | 130%–150% of omitted duties (sobrantes), or a valuation review that can reach the same range (material faltantes) |
| Who controls the outcome | You and your broker, before the pedimento is filed | The customs authority, after an acta de inicio is already open |
None of this requires a disaster to justify the inspection. It requires arithmetic: one man-day at the factory against weeks of demurrage and a fine measured as a percentage of your shipment’s value.
What Should You Actually Do Before Your Next Container Ships?
- Get the factory’s final packing list before loading, not after. If the number changes between quotation and loading day — and it often does — that’s your window to catch it.
- Have someone physically count the cartons against that list at the factory, rather than relying on the same document your broker will use to build the pedimento.
- Flag any “extra” units explicitly, in writing, before the container is sealed — either add them to the invoice or have the factory remove them.
- Send your broker a verified count, not a supplier’s count. The data accuracy standard now sits more squarely on the importer’s side of the relationship than it did before January 2026.
Every step here is checkable with a tally sheet, a camera, and someone standing at the factory who isn’t on the supplier’s payroll — three weeks before your vessel sails, while the fix still costs nothing more than a corrected invoice.
Frequently Asked Questions
What is a sobrante under Mexican customs law? A sobrante is merchandise physically present in your shipment that exceeds what’s declared on your pedimento. Because the excess isn’t covered by any customs documentation, Article 176, fracción X of the Ley Aduanera treats it as a presumption of contraband, regardless of whether the extra units were intentional.
What is a faltante, and how is it different from a sobrante? A faltante is merchandise declared on your pedimento that isn’t physically present. Unlike a sobrante, it doesn’t bring undeclared goods into the country, so it’s treated as inaccurate commercial data under Article 184-A rather than contraband — though it can still trigger a broader valuation review.
What’s the fine if a sobrante is found during customs inspection? Under Article 178, fracción IX, the fine equals 130% to 150% of the omitted duties, or 70% to 100% of the commercial value if the merchandise would otherwise be exempt. If the excess exceeds 10% of your declared value, Article 151, fracción IV also triggers immediate embargo precautorio.
Does every discrepancy trigger an embargo? No. Embargo precautorio for excess merchandise applies specifically when the undeclared or excess amount exceeds 10% of the total value declared in your customs documentation. Below that threshold, the discrepancy is still an infraction, but it’s handled without the automatic seizure.
What is PAMA, and how long does it take to resolve? PAMA (Procedimiento Administrativo en Materia Aduanera) is the formal process that begins once merchandise is embargoed. You have 10 business days to submit evidence, and the customs authority has up to 4 months from the close of that period to issue a final resolution.
Can a previo en origen prevent sobrantes and faltantes? Yes. A previo en origen verifies the physical count against your invoice and packing list before the container is sealed, so any discrepancy is caught and corrected at the factory — before it becomes a pedimento the SAT can challenge.
Count It Before the SAT Does
Every sobrante and faltante in this guide is visible with a tally sheet and a camera, three weeks before your container reaches a Mexican port. The reformed Ley Aduanera has made each one more expensive to discover late — and less forgiving of a broker’s excuse that the numbers came from the supplier.
If your last shipment cleared customs with a discrepancy your broker had to explain after the fact, compare that cost against USD 280 per man-day at the factory. Request a quote for a previo en origen — our inspectors count against your broker’s checklist, not your supplier’s packing list, and the report reaches you while the container is still in the yard.
