Dear Customer,
You can change the Commodity Code the same way you entered it - with paste special (ctrl+enter) to Commodity Codes register. Make sure you save the Item record afterwards.
If it's the Commodity Code itself that is wrong, you can reach it the same way - paste special, then highlight the selected code and press F2 to open it's record. Edit and save. Save the Item record.
Otherwise this register is available from Customs module.
If the problem is the wrong code has been used to some documents, i.e. Invoices - once you change the code on the Item record, the reprinted Invoice should contain the correct code. Please, test this option and see if it works for you.
If the above solutions won't work, please, write back with more detail - what document has been affected, what has been done that is not correct and all possible details to allow us investigate/test the scenario.
HansaWorld Support Team