Most "Mexico manufacturers" are tenants under someone else's permit.
The Mexican government issues IMMEX permits — the legal mechanism that lets a manufacturer import raw materials duty-free for re-export production. Owning one means you're an operator. Renting one means you're a tenant inside a shelter operation.
Shelter operators are common because they're fast: you sign with them, they fold your operation under their permit, and you're "in Mexico" in 60 days. The trade-off is structural. You don't hold the bond. You don't file pedimentos. You can't audit your own customs paperwork. When the broker calls duties wrong, you eat it. When the shelter raises your rate sheet, you sign it.
If your "Mexico shop" can't produce its own IMMEX permit number on demand, you're in a shelter. Ask. The number should look like a 10-digit registration, e.g. 2018-4421.
IMMEX is a bond, a permit, and a paperwork trail.
IMMEX (Industria Manufacturera, Maquiladora y de Servicios de Exportación) lets registered manufacturers temporarily import raw materials, components, machinery, and packaging without paying full duty — provided the finished goods are exported within a defined window.
Three parts that matter operationally:
- The permit. A registration number tied to a specific facility and operator. It's renewed annually. The Mexican Tax Authority (SAT) audits it.
- The bond. A financial guarantee posted with customs against the temporarily-imported inventory. If goods don't leave the country in time, the bond is called.
- The pedimento. The Mexican customs declaration filed for every import and export. It is the audit trail. Whoever's name is on it owns the compliance.
Owning the IMMEX permit means our customs team files the pedimento under our registration. Your name doesn't appear in the chain. If SAT audits, we answer.
C-TPAT is what makes the <24h crossing real.
Customs-Trade Partnership Against Terrorism (C-TPAT) is a U.S. CBP program for importers that meet a defined supply-chain security standard. It's voluntary. It's expensive to qualify. And once you're in, your shipments move through expedited "trusted trader" lanes with reduced inspection rates.
For an apparel program, the practical effect is simple: instead of trucks sitting at Otay Mesa for 6-18 hours waiting to cross, C-TPAT-certified shipments are pre-cleared. You get a known crossing window, you can tell your warehouse to schedule receiving, and your downstream parcel injection doesn't miss the carrier's afternoon cutoff.
Sub-24h Tijuana floor → San Diego dock means a drop printed Monday is in DTC parcel network by Tuesday. Without C-TPAT, plan for Wednesday or Thursday — and hope the line at customs cooperates.
Duty math starts at the bill of materials.
USMCA replaced NAFTA in 2020. For apparel, the headline is "yarn forward" — qualifying garments must use yarn produced in a USMCA country (US, Canada, or Mexico) to enter the U.S. duty-free.
That sounds like a constraint. It's actually a planning lever. If you classify your bill of materials at design stage — yarn source, fabric construction, trim origin — you can route components to qualify. Shirts cut from USMCA-yarn cotton, sewn in Tijuana, exported to the U.S. enter duty-free under USMCA. Same garment using imported yarn pays MFN (Most Favored Nation) duty rates of 16-32% depending on classification.
Pedimento (MX export), Bill of Lading (carrier handoff), CBP entry summary (US import), and a USMCA Certificate of Origin if you're claiming preferential treatment. Missing the certificate is the #1 reason brands pay duty they didn't need to.
22-38% landed savings, on average — measured per SKU.
The savings come from three stacked effects: (1) labor arbitrage on cut-and-sew, (2) duty avoidance under USMCA, and (3) freight optimization from being 30 miles south of San Diego instead of overseas.
Brands often see only one of these levers in a typical "Mexico quote." You should see all three modeled at quote time, with the assumptions documented per SKU. If a vendor can't show you the duty math line-by-line, they're probably routing through a shelter and not USMCA.
The five files that need to be in your shared drive.
Every cross-border apparel program should produce these monthly. If yours doesn't, switch operators.
- 01IMMEX permit certificateAnnual. Confirms the permit is current and tied to the operating facility.
- 02PedimentosPer-shipment. Filed both directions (MX export, US import).
- 03USMCA Certificates of OriginPer-shipment. Required if claiming preferential duty treatment.
- 04WRAP audit reportAnnual. Independent labor/working-conditions certification. Required by most national retailers.
- 05C-TPAT validationRe-validated every 4 years. CBP-issued certificate of trusted-trader status.
Three failure modes most brands learn the expensive way.
IMMEX bonds are tied to a maximum dwell time. If finished goods sit in a Mexican warehouse past the window without exporting, customs calls the bond. Brands that shelter often don't even know this clock is running. Operators that own the bond manage it daily.
A USMCA-qualifying garment without the certificate of origin pays full MFN duty. We've seen brands lose 16-22% margin on shipments because their broker forgot to file. Automate the certificate alongside the pedimento — every shipment, no exceptions.
National retailers (Target, Walmart, Costco, REI) require valid WRAP certification on file. Lapsed audit = paused PO. Audit annually, share the report proactively, don't wait for the retailer to ask.