You can't hide the product code, but you can shrink it to 4 digit:
  • Go to the Menu "Configuration / General information",
  • Select option : "18. Display only 4 characters in the product code printed on the invoice",
  • Save.
When selecting to print only the last 4 digits of the product code on the invoice, the complete code will show in the order history and in the Point of Sale.
  • Go to "Configuration"/"Company management"
  • Go to "Taxes"
  • Click on the next available line (as you are about to add new tax)
  • In the "Management of tax groups" window you can modify the tax number and the GL code.
  • Save and exit.

Note: In "Tax group Management" the change will not be visible right away, you have to restart the "Company maintenance" module.