The rule for handling trade with itself is a mix of hard facts and assumptions/preferences:
- country cannot export to itself
- country cannot trade with own free zone when it follows the general trade system
- if there are only imports from itself (no matter whether General or Special trade system) it's most likely re-imports. In this case, the re-imports would be created.
- when country follows the special trade system, trade with itself can be explained as trade with its free zones. Please refer to the IMTS Compiler Manual https://unstats.un.org/unsd/publication/SeriesF/seriesf_87e.pdf for more information about trade systems.