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Two characters. That is the entire field. In the system that builds your pedimento (Mexico's customs declaration), it looks like a dropdown, and it gets treated like one. In the Ley Aduanera, those two characters are the statement of what your operation legally is, and every document, deadline and duty consequence downstream follows from them.
The catalog is Apéndice 2 of Anexo 22 of the Reglas Generales de Comercio Exterior, the instructivo, or official filling instructions, that govern how a pedimento is completed. It runs to roughly ninety keys. Most operations use eight or nine of them, misuse two, and have never read the appendix that defines any of them. This is the map.
What the clave declares, and what it does not
Start with a distinction that most operators collapse, because the two fields sit next to each other on the form.
Field 3 of the pedimento is the CVE. PEDIMENTO, the clave, defined by Apéndice 2. Field 4 is the RÉGIMEN, the customs regime, defined by Apéndice 16. They are related but they are not the same declaration. The regime says which of Mexico's customs regimes the goods are entering. The clave says which specific operation, within or across those regimes, is being performed. One regime carries many claves. A key like V1 spans several regimes in a single definition, because a virtual transfer is simultaneously a return for one party and a temporary import for another.
On paper, then, choosing a clave is a lookup. You find the operation, you take the two characters, you move on.
In practice, the clave is the one declaration on the pedimento that is hardest to undo. The instructivo is explicit in the rectification section of Anexo 22: rectification of the clave de pedimento is not permitted when it implies a change of regime. A wrong fracción arancelaria can be rectified. A wrong value can be rectified. A clave that put your goods in the wrong regime cannot simply be corrected on a second filing, because the correction would change what the operation legally was. That is why this field deserves more attention than its size suggests.
The families, before the keys
Reading Apéndice 2 key by key is how people give up on it. Read it by family and it collapses into something a team can hold in its head.
The definitive family covers goods entering to stay or leaving for good, plus the corrections and special cases attached to that permanence. The virtual operations family covers movements that happen on paper between authorized parties without the goods crossing anything. The temporary family covers goods entering or leaving for a defined period and a defined purpose. The IMMEX family is a distinct block for manufacturing under the program. The depósito fiscal family, Mexico's bonded warehousing regime, covers both introduction and extraction, including a separate treatment for the automotive industry. The recinto fiscalizado estratégico family covers the strategic bonded facility regime. The transit family covers movement of goods under customs control between customs offices. And two administrative keys sit outside all of it: R1 for rectifications, and CT for the complementary pedimento.
Locate the family first and the number of plausible keys drops from ninety to a handful.
Definitive: A1, A3, and the key that is not what its letter suggests
A1 is the workhorse. Apéndice 2 defines it as definitive import or export, and the first two cases it lists are the ones everyone knows: foreign goods entering to remain in national territory for unlimited time, and goods leaving to remain abroad for unlimited time. What most operators do not know is how much else A1 absorbs. Definitive imports of new and used vehicles. Definitive imports of goods withdrawn from a recinto fiscalizado estratégico adjoining the customs office. And a specific IMMEX carve-out worth memorizing: the return of packaging, labels and brochures that were temporarily imported under an IMMEX program and are used to export national merchandise goes under A1, not under the IMMEX return key.
A3 is regularización, the lawful route back into compliance, and it is the key that exists because operations go wrong. It covers goods already in national territory that never completed customs formalities, goods that entered under temporary import and whose term expired (including the scrap they generated), machinery without documentation to prove its lawful import or presence, and goods whose recinto fiscalizado estratégico term expired. A3 is not an error key in the administrative sense. It is the lawful path back for a situation that has already gone irregular, which is a different thing.
T1 is the correction most worth making, because the letter misleads. T1 is not a transit key. Apéndice 2 places it in the definitive regime and defines it as import and export by courier and parcel companies, under the simplified procedure of regla 3.7.5. The transit keys are elsewhere: T3 for internal transit, T6 for international transit through foreign territory, T7 for international transit through national territory, and T9 for transmigrant transit.
Also in this family: C1 for definitive imports into the northern border strip and border region, D1 for return by substitution of defective goods, K1 for withdrawal from a customs regime and return of goods, P1 for reexpedition from the border region into the interior, S2 for goods imported to be returned in the same state under Article 86 of the Ley Aduanera, and GC, the global complementary pedimento used for annual value adjustments when there are contributions to pay.
IMMEX: IN, AF and RT, and why the first two are not interchangeable
The IMMEX block in Apéndice 2 has three keys, and the most common error in the entire appendix lives between the first two.
IN is the temporary import of goods that will undergo transformation, elaboration or repair. Inputs. Materials that become part of something. It also covers the return to Mexico of goods that were transformed here and then rejected abroad for being defective or off-specification, within a year and unmodified.
AF is the temporary import of fixed assets under IMMEX, the machinery and equipment covered by Article 108, fracción III of the Ley Aduanera. Not inputs. The production line, not what runs through it.
They are different keys because they carry different permanence periods, different discharge obligations, and different treatment when the company later decides to keep the goods. Bringing in a machine under IN because the input key was the one the team knew is not a clerical variation. It puts an asset into an inputs balance, where it will sit against a return deadline it was never meant to meet.
RT is the return of goods under IMMEX: goods transformed, elaborated or repaired under the program going back abroad, and foreign goods returning in the same state. Note the exclusion built into the definition, the mirror of the A1 carve-out above: packaging, labels and brochures temporarily imported under IMMEX and used to export national merchandise are expressly excluded from RT and must go under A1.
And note what RT is not. The return of goods in the same state outside of IMMEX is H1, a different key in a different family. Two operations that a warehouse describes with the same English word, "return," and that the appendix separates completely.
Virtual operations: V1 and its relatives
The virtual family is where paper moves and cargo does not, and it is the family most likely to be filled in by whoever filled it in last time.
V1 is the broad one. Apéndice 2 defines it as transfers of merchandise, covering virtual temporary import, virtual introduction to depósito fiscal or to a recinto fiscalizado estratégico, virtual return, and virtual export by national suppliers. It covers eleven distinct cases, including IMMEX companies transferring temporarily imported goods to other IMMEX companies, transfers to and from strategic bonded facilities, sales between foreign residents of goods physically delivered in Mexico, and virtual transfers of scrap between IMMEX companies.
Around it sit the specialized versions. V2 for transfers of goods imported with a cuenta aduanera. V5 for transfers by certified companies, the virtual return for definitive import. V6 for goods subject to cupo, the tariff quota system. V7 for the sugar sector. V9 for donations of scrap or obsolete machinery by IMMEX companies. VD for virtual operations that fit none of the above. And G9 for the virtual withdrawal from a non-adjoining recinto fiscalizado estratégico for definitive import by residents in national territory.
One operational detail from the instructivo that saves an argument: in virtual transfers under V1, V2, V5 and V6, the INCOTERM field does not need to be filled in.
Changing your mind: F4, F5, and the correction that is not available
Two keys govern what happens when temporary stops being temporary, and the brief version most teams carry ("F4 or F5, whichever the system takes") is wrong in a way that matters.
F4 is the change of regime for inputs, or for goods that were temporarily exported. The cases it covers are temporary to definitive for goods subject to transformation, elaboration or repair by an IMMEX company before the return deadline expires, virtual temporary to definitive export, scrap from temporarily imported or exported inputs under Articles 109 and 118 of the Ley Aduanera, and parts and components by the certified auto parts industry.
F5 is the change of regime of temporarily imported goods to definitive in the other cases: fixed assets under an IMMEX program before the return deadline, goods from conventions and international congresses, the goods of Article 106 with specific exceptions, and used vehicles ten or more years old under regla 3.5.8.
The dividing line is the same one that separates IN from AF. Inputs go one way, assets go the other. A company that regularizes a machine as if it were an input has not chosen an equivalent path.
And here the rectification limit returns with teeth. If the clave you filed put the operation in the wrong regime, a rectification will not fix it, because the instructivo does not permit rectifying a clave when doing so implies a change of regime. What remains is a different and slower route, usually a regularización under A3 with the contributions and consequences that carries.
Where the mis-keying actually happens
In our work across the corridor, the pattern is consistent and it is almost never ignorance of the appendix. It is inheritance. A clave gets chosen correctly for one operation, the operation becomes routine, the routine becomes a template, and then the business changes underneath the template. A plant that used to export everything starts selling domestically. An IMMEX operation buys equipment instead of leasing it. A supplier relationship becomes a virtual transfer. The template does not know any of that happened, and nothing in the clearance process asks.
That is why the audit here is not a training session. It is a periodic reconciliation between what the operation actually does and what the two characters say it does.
Run it this way. Pull the distinct claves used across your last ninety days and count the operations under each. For every clave in that list, open Apéndice 2 and read the cases listed under it, not the title. Most mis-keying survives because the title of the key sounds right and the cases underneath it do not match. Then check the specific pairs that carry the most exposure in your operation: IN against AF if you import equipment, RT against H1 and A1 if you return anything, F4 against F5 if you have ever changed a regime, and any clave that appears exactly once or twice, because a key used rarely is a key nobody has verified.
Across more than 190,000 customs operations a year at 39+ ports and three Patentes Nacionales, the operations that never argue about a clave are not the ones with the best software. They are the ones where somebody reads the appendix when the business changes, instead of when the cargo stops.
Two characters. They decide the regime, the documents, the deadlines and the exposure, and they are the hardest thing on the pedimento to take back. Worth knowing which two you are declaring.
Talk to a Joffroy expert about a clave de pedimento review of your last ninety days of operations.
TRADE. UNDER CONTROL.
