On October 13, 2026, Mexico's Senate passed a reform to the Customs Law (Ley Aduanera) that removes the 50% undervaluation threshold customs needed before it could seize an import as a precaution; with both chambers on board, it takes effect January 1, 2027. That's according to the Mexican Senate, which sent the decree to the Executive.
If you're a foreign brand shipping inventory into Mexico, the short version is this: from 2027, a smaller gap between the value you declare and the value Mexican customs determines can be enough to hold your goods. For an ecommerce brand, a held shipment is a stockout.
The timeline
- September 8, 2026. The Executive sent the initiative to Congress as part of the 2027 Economic Package, Mexico's annual budget and tax bundle, according to Infobae.
- October 6, 2026. The Chamber of Deputies passed it (Bloomberg Línea), 334 to 119 in the general vote (Infobae).
- October 13, 2026. The Senate passed it 66 to 37 with one abstention in the general vote, and 66 to 34 on the specific articles (Senate).
- As of October 19, 2026, it is still pending publication in Mexico's Official Gazette (DOF); we checked the October 13–19 editions.
The reform amends articles 144, 151, 153, 154, 177 and 185 of the law, plus the second transitory article (TaxToday México).
What changes on January 1, 2027
Three terms first. Undervaluation means declaring a lower value than the one legally due. Transaction value is, put simply, the price actually paid or payable for the goods; Mexico's customs value, the base for your import duties and taxes, starts from it. A precautionary seizure (embargo precautorio) means customs holds your goods while the value question is resolved, and you can't sell them in the meantime.
| Topic | Through December 31, 2026 | Under the reform |
|---|---|---|
| Precautionary seizure for undervaluation (art. 151, section VII) | Applies if the declared value is 50% or more below that of identical or similar goods | Threshold removed (Senate) |
| Estimated-price guarantee (art. 86-A) | If you had posted it, no seizure on this ground | Exception removed (TaxToday México) |
| Replacing the seizure with a guarantee (art. 154) | Already possible (TaxToday México) | Gap under 20%: cash deposit or customs guarantee account. 20% or more: cash only (Bloomberg Línea) |
| Presumed infraction under duty-deferral regimes (art. 177, section XII) | Value gap of 50% or more | Value gap of 20% or more (Senate) |
What's still undefined: the new percentage
Removing the 50% threshold doesn't mean any gap at all will trigger a seizure. Before the reform takes effect, administrative rules must spell out which goods, which procedures and, where applicable, which percentages apply, the Senate explained. They must be published in the DOF by December 31, 2026 (TaxToday México).
So the threshold moves out of the statute and into rules set by the authority, possibly by type of goods (TaxToday México). That discretion is precisely why part of the opposition voted against it (Senate).
If you read that the threshold "dropped from 50% to 20%," two things got mixed up. 20% is the new trigger for a presumed infraction under article 177, which covers regimes that defer payment of duties, such as IMMEX (Mexico's program for manufacturers and exporters) or bonded warehousing (EY). It's also the cutoff for how you can replace a seizure. The seizure threshold itself isn't lowered: it's removed.
What it means if you ship inventory into Mexico
- Declare the real transaction value. What was actually paid, not what "works" on the invoice. If you sell to your own Mexican entity or distributor, document how that intercompany price was set.
- Keep the value file complete. Commercial invoice, proof of payment, freight and insurance. If your price is below market because of a closeout or a volume discount, keep the purchase order or the email where it was agreed: that's how you substantiate the value if it's challenged.
- Budget for cash. If the gap is 20% or more, the only way to release the goods is a cash deposit covering the taxes on that difference (Bloomberg Línea). That money is tied up until the case is resolved.
- A seizure is a stockout. Held goods don't sell. For shipments landing from January 2027 on, size a buffer for your imported SKUs; here's how to calculate safety stock.
- Talk to your Mexican customs broker before December. The licensed customs broker (agente aduanal) clears your goods and files the pedimento, Mexico's customs entry, where the value is declared. Ask them to review the values you declare on recurring shipments and to flag the new rules when they come out. If you're new to the role, start with what a customs broker does in Mexico.
What a 3PL does and doesn't do
To be straight with you: a 3PL doesn't fix a customs valuation. Ecommex is not a customs broker and not a bonded customs facility (recinto fiscalizado). The value is declared by the importer with their broker, and the responsibility is the importer's.
What our import service does: we coordinate with customs brokers, ocean carriers and domestic transport; your pedimentos, invoices and certificates live in your portal; and we receive the goods at our warehouse in Zapopan, in the Guadalajara area, counting them against the commercial invoice. That doesn't replace your broker, but it keeps your documents in order and tells you early if what arrived doesn't match what you were billed for.
FAQ
Is the reform already in force? No. Congress has passed it, but as of October 19, 2026 it was still pending publication in the DOF. It takes effect January 1, 2027 (Senate).
How big a value gap will trigger a seizure? Not known yet. The administrative rules will define it, and they must be published by December 31, 2026 (TaxToday México).
Can I get seized goods back? Yes, by replacing the seizure with a guarantee. If the ruling goes your way, the guarantee is released or the deposit refunded (Senate).
If you're a brand shipping inventory into Mexico and need it received, counted against the invoice and ready to ship to customers, see how our 3PL in Mexico works alongside our import logistics into Mexico.