hide tax code in accounting document after miro posting

Hi Expert,

my customer is using SAP 4.5B, when using miro to do posting and i select vendor, line item and unplanned delivery cost with same tax code P0.

Then i post the document and when i display the accounting document found that:

tax code

31 vendor **

81 g/l expense (blank)

81 unplanned delivery cost P0

as all tax code i choose is P0 and its should be all P0 or all together will blank.

standard sap will show ** because got more than 2 different tax code. but now is all same tax code.

expert, please advice is this can be configure?

and please advice how to configure

Thanks

regards,

ng chong chuan