In the customs code table, the 5th-8th digits are the Gregorian calendar year when the customs accepts the declaration, the 9th digit is the import and export mark ("1" means import and "0" means export), and the last 9th digit is the serial number.
The following is an introduction to the customs numbering rules of customs declaration forms:
The customs number of the customs declaration form is 9 digits, of which 1-2 digits are the customs number that accepts the declaration (the last two digits corresponding to the customs code in the customs code table), the third digit is the last/kloc-0 digit of the four digits of the Gregorian calendar year that the customs accepts the declaration, and the last six digits are the serial number.
The import declaration form and the export declaration form shall be numbered separately to ensure that each declaration form can be uniquely identified according to the import and export situation in the same calendar year.
The customs number of the customs declaration form is 18 digits, where the number 1-4 is the customs number that accepts the declaration (corresponding customs code in the customs code table), the numbers 5-8 are the Gregorian calendar year when the customs accepts the declaration, the number 9 is the import and export mark ("1" is the import and the number 0 "is the export), and the last 9 digits are the serial number.
Refer to Baidu Encyclopedia-Customs Number for the above information.