The open customs warehouse module provides functions for handling duty-unpaid goods. Duty-unpaid goods are indicated as such. PROLAG®World carries out analyses of duty-unpaid goods. There is a dialog function for changing the goods from duty-unpaid to duty-paid with the radio data terminal on the forklift, or example. This transaction is completed with name, time and all further data. The conversion of duty-unpaid goods to duty-paid goods can be reported via an interface to the host system. A customs transaction number is allocated at storage-in and is retained in all booking transaction right up to the history. The stock levels and characteristics of duty-unpaid or duty-paid goods can be referenced any time or printed as a list.