You can provide the MRN of only one transit as previous document in the import declaration (updated 9 June.2022)

When you are completing an import declaration via the service Import declarations for businesses – special procedures, you can provide the MRN of only one transit as previous document. For example, if you have goods that arrived with two transit accompanying documents you cannot declare them in one import declaration, both transits must be submitted in separate import declarations. 

However, when you are completing an import declaration in the Customs Clearance Service, you can provide the MRN of several transits as previous document.

More information:
The previous document must be provided in the import declaration
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