A guide for U.S. companies with a plant in Mexico in the electrical, electronics or automotive sectors. The short answer: the decree published in the evening edition of the DOF on April 23, 2026, in force April 24, amended article 5 of the PROSEC Decree and made several flat and plate steel tariff lines duty-exempt for those three sectors. At the same time it set duties of 5% to 35% on 185 lines of the general tariff. For an IMMEX plant that exports to the United States, the change touches directly what it pays on export under USMCA.
What changed
- General tariff (article one): 185 lines at 5% to 35%, in chapters for chemicals, paper, textiles and footwear, steel and aluminum, glass, auto parts and consumer goods. Preferential treatment stays for goods originating in treaty countries, if the rule of origin is met.
- PROSEC (article two): in article 5 of the PROSEC Decree, lines under headings 72.08, 72.09, 72.11 and 72.25 (with technical conditions on thickness, carbon or boron content and steel type) become exempt for the electrical, electronics, and automotive and auto-parts sectors.
- In force: since April 24, 2026, with no published end date.
Why it matters to an IMMEX plant that exports to the United States
Under IMMEX, steel enters temporarily without paying the general import duty. But when the finished product is exported to the United States or Canada, USMCA article 2.5 limits duty deferral: the plant must pay the Mexican duty on the non-originating inputs, with the adjustment the agreement allows. If the company also holds PROSEC in the right sector, that duty is calculated at the PROSEC rate. On the lines the decree made exempt, the payment drops to zero. Without PROSEC, or with PROSEC in another sector, the general rate applies, and it went up in January 2026 for steel from countries without a treaty.
What to check in your program
- That the company holds a valid PROSEC in the sector that matches its finished product (electrical, electronics, or automotive and auto parts). The benefit is by sector, not by company.
- That the steel lines you import match the ones the decree exempted, conditions included: a millimeter of thickness or the carbon content can take a product out of the exemption.
- That the PROSEC annual report is filed; without it the program is suspended and the exemption does not apply.
- How PROSEC is declared on the pedimento and how the article 2.5 payment is calculated on export: this is where the benefit is won or lost.
- If the steel is not on your sector's list, whether a Rule 8 permit fits as a complement.
Risks we see
- Plants still paying the general rate because their customs broker did not walk through the change, or applying the exemption without the right sector in the program.
- Exports to the United States with the article 2.5 payment calculated at the old rate, creating credit balances that are hard to recover, or the reverse, omitted payments that surface in an audit.
- PROSEC programs suspended over the annual report, discovered when the exemption is attempted.
Frequently asked questions
Does my company need PROSEC if it already has IMMEX?
They are separate, compatible programs. IMMEX defers the duty on temporary imports; PROSEC lowers the duty on definitive imports and in the USMCA article 2.5 calculation when exporting to the United States or Canada. Most export plants with inputs from Asia need both.
Does the exemption cover all steel?
No. Only the lines listed in article 5 of the PROSEC Decree for each sector, with their conditions. Other steel keeps the previous PROSEC rate or the general rate.
What if my PROSEC is in another sector?
The exemption does not apply. Registration in the right sector or a program change can be analyzed, as long as the plant makes products of that sector.
General information, updated October 2026. It does not replace legal advice for a specific case.
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