You'll have the option of entering all company/business details whilest booking. Simply uncheck Invoice details same as contact details on the contact details page and all required fields will pop out.
Please note that due to privacy restrictions it is only possible to add your company details during booking. Changing the details afterwards (eg. in MijnTix) will not update your existing invoice.
Forgot to enter your company details? Unfortunately, there is nothing we can do at this point.