How do notes use cross references to other classes?

Notes use cross references to point from an exclusion in one note to the class where the excluded activity is classified, using the word see followed by a class code. A cross reference in an excludes list is therefore not a suggestion to look elsewhere for more information. It is part of the definition of the category, stating the other side of the boundary. The note that contains the exclusion, and the note that contains the corresponding inclusion, must be read as a pair, and the pair defines the boundary between the two classes.

What form does a cross reference take?

A cross reference in the published notes takes the form of an exclusion statement, followed by the words see and a code. In the note for class 01.11, for example, Eurostat states growing of rice, see 01.12, growing of sweetcorn, see 01.13, growing of maize, lupines or kale for fodder, see 01.19, and growing of oleaginous fruits, see 01.26. In the note for class 01.13, Eurostat states growing of spices and aromatic, drug and pharmaceutical crops, see 01.28, and growing of mushroom spawn, see 01.30. In the note for class 01.15, Eurostat states preparation of tobacco leaves by a third party, see 01.63, and manufacture of tobacco products, see 12.00. Each reference gives a single class code, in the same version as the note, and each reference must be followed to the note for that class, where the inclusion should be confirmed.

The form is consistent across the notes in Part 3 of the manual, as shown by the agriculture examples. A cross reference can point to a class in the same group, in a different group in the same division, in a different division in the same section, or in a different section, as the tobacco manufacture reference to division 12 shows. The distance of the reference does not change its function. In every case, the reference states the class where the excluded activity is classified, and the pointed to note must be read to confirm the inclusion and any conditions stated there. A reference that points to a class in another section must be followed across the section boundary, with the section notes for both sections read where the boundary is unclear.

Starting note	Exclusion and cross reference stated by Eurostat	Pointed to note to read
01.11	Growing of rice, see 01.12	Note for 01.12, growing of rice
01.11	Growing of sweetcorn, see 01.13	Note for 01.13, includes also sweetcorn
01.13	Growing of mushroom spawn, see 01.30	Note for 01.30, plant propagation
01.15	Manufacture of tobacco products, see 12.00	Note for 12.00, manufacture of tobacco products

How is a chain of cross references followed?

A chain must also be followed in the correct version. A cross reference in a note for NACE Rev. 2.1 points to a class in NACE Rev. 2.1, and a cross reference in a note for NACE Rev. 2 points to a class in NACE Rev. 2. The codes in the two versions may differ, and a reference followed in the wrong version will lead to the wrong class. The version of the manual consulted, the 2025 edition (FIXED) for the new version, must be stated beside the reference, and the pointed to note must be read in the same edition. A reference quoted without a version label cannot be verified, because the same code may denote a different class in the other version.

What is the difference between a cross reference and a correspondence table row?

A cross reference is a statement inside a note, pointing from an exclusion to the class where the excluded activity is classified, within the same version. A correspondence table row is a statement in a table, showing the relationship between a class in one version and classes in the other version, with a type. The two must not be confused. A cross reference does not show a move between versions, and a correspondence row does not show a boundary inside one version. A reader who follows a cross reference to a class in the same version, and then checks the correspondence table for that class, is doing two different checks: first, the boundary inside the version, and second, the relationship between versions for the class found. Both checks are needed where a comparison over time is in question, and neither check replaces the other.

The distinction also matters for citation. A boundary statement must be cited to the note that contains the exclusion and the cross reference, with the pointed to note cited for the inclusion. A version relationship must be cited to the correspondence table, with its version and direction stated, and to the notes for the scope in each version. A citation that gives only the cross reference, for a version relationship, or only the table row, for a boundary inside one version, cites the wrong source for the question, and the conclusion drawn from it cannot be verified from the citation given.

What does a cross reference not do?

A cross reference does not assign a code, and it does not confirm an entry. It points from one note to another, inside the same version, as part of the definition of the categories. The assignment of a unit, and the confirmation of an entry, remain separate steps, made by the institute or register that holds the record. A reader who follows a cross reference chain to a class has found a category that covers an activity, as stated in the notes. That reader must still apply the classification rules to the unit, where the unit carries out several activities, and must still confirm the entry with the institute or register, before presenting a code as the code for a specific business or activity.

Follow each cross reference to the note it points to, confirm the inclusion there, and confirm any entry with the national statistical institute or the business register that holds the record.