20.9. Goods for repair and service operations. Processing should be clearly delimited from simple service operations or repair. A repair is defined as “the restoration of goods to their original function: this may involve some rebuilding or enhancements”. The following examples may facilitate the identification and delimitation of repair and service operations:
- Simple replacement of part of an item indicates that a repair transaction might have been carried out; on the other hand, if it results in an really improved item, repair is a process
- Repair of damage to goods incurred during transport
- Repainting should be treated as repair/maintenance; however, the painting of unpainted goods should be treated as processing
- For aircraft, technical maintenance activities that are carried out owing to legal requirements (e.g., controls, mandatory periodic replacements)
- Testing, adjusting, regulating or certification of goods (e.g., aircraft, machines, apparatus, vehicles)
- Simple ironing, washing, cleaning, drying operations
- Simple packaging operations
- Simple sorting, sifting, weighing, dividing and filtering of goods
20.10. Difficulties. In practice, many borderline cases might exist where repairs and service operations can be difficult to differentiate from processing. Such borderline cases encompass, for example, a repair in which, as replacement, part of a new model with better performance is used, and the partial refitting of a ship or aircraft during repair. Cases that involve high-value goods such as ships and aircraft can have a significant impact on the value of imports and exports and should therefore be reviewed on an individual basis. The users should be informed appropriately about their recording.
 In the past, this list of examples has been in use within the European Union. While it might require further review and elaboration, it appears to be largely acceptable to most countries.
 For further details on the recording of aircraft (and ships), see chap. XXIII.