How to Import from Mexico to the U.S.: A Step-by-Step Guide

Importing from Mexico is not one transaction. It is two clearances stitched together. Your goods have to legally leave Mexico as an export, then legally enter the United States as an import, and the paperwork on each side has to agree. Most delays at the San Diego and Otay Mesa border are not caused by trucks. They are caused by a classification, a bond, or a partner-agency requirement that was not handled before the freight moved.

This guide walks the full sequence the way a licensed customs broker actually runs it: gathering supplier documents, classifying the goods under the HTS, filing the ISF, securing a customs bond, transmitting the entry through ACE, clearing any partner government agency requirements, physically crossing at Otay Mesa, and releasing the shipment for delivery. It applies whether you move cargo one direction or, as many border operations do, both directions at once.

Understand the Two-Sided Reality: Mexican Export and U.S. Import

Every northbound shipment crosses two legal thresholds. On the Mexican side, the goods must be cleared for export with a pedimento, the official Mexican customs declaration prepared by a Mexican customs broker (agente aduanal). On the U.S. side, the goods must be entered with U.S. Customs and Border Protection (CBP) under an entry filing. These are separate filings governed by separate authorities, and each has its own classification code: the fraccion arancelaria in Mexico and the HTS number in the United States.

This is why border brokerage is genuinely bidirectional. A U.S. import is a Mexican export, and a Mexican import is a U.S. export. At the San Diego and Otay Mesa crossing, coordinated clearance on both sides is the difference between a truck that rolls through and a truck that sits. The importer of record on the U.S. side is legally responsible for a correct, complete entry and for paying duties, taxes, and fees, so the U.S. filing has to be right regardless of what happened on the Mexican side.

• Mexican side: pedimento (export declaration) prepared by a Mexican agente aduanal, goods classified by fraccion
• U.S. side: CBP entry filed under an HTS classification by the importer of record or their licensed customs broker
• Both filings must describe the same goods, quantities, and values consistently

Step 1: Gather and Verify Supplier Documents

The entry is only as good as the documents behind it. Before anything is filed, assemble a complete and internally consistent document set from your Mexican supplier. The core documents are the commercial invoice, the packing list, and the bill of lading or, for truck freight, the carrier documents. For border truck moves through Otay Mesa the controlling transport document is typically the pedimento and carrier paperwork rather than an ocean bill of lading.

The commercial invoice carries the weight. It must show the seller and buyer, a clear description of the goods, quantity, unit and total value, currency, country of origin, and the terms of sale (Incoterms). Country of origin is not the same as the country you are shipping from. Goods can ship from Mexico but originate elsewhere, and origin drives both duty rate and eligibility for preferential treatment under the USMCA. If you intend to claim USMCA duty-free treatment, you need a valid USMCA certification of origin with the required data elements from the certifier.

• Commercial invoice: parties, goods description, quantity, value, currency, country of origin, Incoterms
• Packing list: piece count, weights, dimensions, how the goods are packed
• USMCA certification of origin, if claiming preferential duty treatment
• Any manufacturer affidavits, mill certs, or spec sheets a partner agency may require

Step 2: Classify the Goods Under the HTS

Classification is the single most consequential decision in the entry. Every good imported into the United States is assigned a number from the Harmonized Tariff Schedule of the United States (HTSUS). That 10-digit number determines the duty rate, whether antidumping or countervailing duties apply, whether a partner government agency has jurisdiction, and whether USMCA or another program can reduce the duty. A wrong classification is not a clerical error. It can mean underpaid duties, penalties, and cargo holds.

Classification follows the General Rules of Interpretation and turns on what the product actually is: its material composition, its function, and how it is presented. Two products that look similar can sit in different headings with materially different duty rates. When a classification is genuinely uncertain, the importer can request a binding ruling from CBP so the treatment is settled in advance. On the Mexican export side the same goods are classified under the fraccion arancelaria, and the two classifications should be reconcilable because both derive from the same international Harmonized System at the 6-digit level.

• The HTS number sets the duty rate, PGA flags, and program eligibility
• Classification depends on composition, function, and form, not on the product’s marketing name
• Request a CBP binding ruling when the correct heading is genuinely unclear
• The U.S. HTS and Mexican fraccion share the first 6 digits under the Harmonized System

Step 3: File the ISF (When the Goods Move by Ocean)

Importer Security Filing, known as ISF or 10+2, is an ocean-freight requirement. It applies to cargo arriving in the United States by vessel, and it must be transmitted to CBP no later than 24 hours before the cargo is laden aboard the vessel at the foreign port. A late, inaccurate, or missing ISF can carry a liquidated damages claim of up to 5,000 dollars per violation, and it can trigger exams and holds.

This step matters for the way you plan a Mexico supply chain. A large share of Mexico-to-U.S. freight crosses by truck at land ports like Otay Mesa, and truck border crossings are not subject to the ISF requirement. But if any leg of your Mexican-origin cargo moves by ocean, for example goods that arrive at a Mexican port from a third country and then continue, the ISF obligation attaches to that ocean movement. Know your actual mode before assuming ISF does or does not apply.

• ISF 10+2 applies to ocean cargo only, filed at least 24 hours before lading at the foreign port
• Penalty exposure runs up to 5,000 dollars per violation for late or inaccurate filings
• Truck crossings at Otay Mesa are not subject to ISF
• Confirm the actual transport mode for every leg before deciding ISF does not apply

Step 4: Secure a Customs Bond

To file a formal entry, the importer of record must have a customs bond on file with CBP. The bond is a financial guarantee that duties, taxes, and fees will be paid and that the importer will comply with customs regulations. It does not replace the duties you owe. It guarantees them. There are two common forms: a single transaction bond that covers one shipment, and a continuous bond that covers all of an importer’s entries at all ports for a 12-month period.

The activity code that applies to standard importations is Activity Code 1, the import bond. For anyone importing from Mexico with any regularity, a continuous bond is usually the better economic and operational choice because it covers unlimited entries during the term and avoids arranging a new bond for every load. A continuous bond also satisfies the ISF bond requirement for ocean shipments. Formal entries, generally required for commercial shipments valued over 2,500 dollars, are where the bond requirement bites; low-value informal entries are treated differently.

• Single transaction bond: covers one shipment, often sized to duties plus taxes and fees
• Continuous bond: covers all entries at all ports for 12 months, Activity Code 1 for imports
• Regular Mexico importers usually benefit from a continuous bond
• The bond guarantees payment and compliance; it is not a substitute for the duties owed

Step 5: File the ACE Entry, Clear PGA Requirements, Cross Otay Mesa, and Deliver

The entry itself is transmitted electronically to CBP through the Automated Commercial Environment (ACE), the system of record for U.S. imports. The broker files the entry and the entry summary, which state the HTS classification, declared value, country of origin, any USMCA or other program claims, and the duties, taxes, and fees due. Standard fees include the Merchandise Processing Fee (MPF) and, for ocean shipments through a listed port, the Harbor Maintenance Fee (HMF); MPF is subject to statutory minimum and maximum amounts per formal entry. Commercial shipments over 2,500 dollars generally require a formal entry, while many shipments at or under 800 dollars can qualify for informal or Section 321 de minimis treatment.

Before or alongside the CBP filing, any partner government agency (PGA) requirements have to be satisfied. If the goods fall under FDA (food, dietary supplements, cosmetics, medical devices), USDA (agricultural products, certain plants and animal goods), EPA, or another agency, that agency’s data and any prior notice or permits must be transmitted with the entry. Missing a PGA requirement is one of the most common causes of a hold at Otay Mesa. Once the entry is filed and PGA conditions are met, the truck presents at the Otay Mesa port of entry, CBP either releases the shipment or selects it for exam, and on release the goods proceed to the delivery point. After release, the entry summary is finalized and duties are paid, and CBP later liquidates the entry as the final accounting.

• ACE is the electronic system where the entry and entry summary are filed with CBP
• MPF and, for applicable ocean cargo, HMF apply; formal entry generally required above 2,500 dollars
• Section 321 de minimis can apply to qualifying shipments valued at 800 dollars or less
• PGA data (FDA, USDA, EPA, and others) must accompany the entry when the goods are regulated
• At Otay Mesa the truck is presented, CBP releases or exams, then the shipment moves to delivery