Department of Inland Revenue has published a Application Form for Profile Update (For Company).
All taxpayers are required to update their profile with the relevant activity code in the IRD system. This can be done by updating the profile information via e-Service or by sending the requested information and documents to the Commissioner of Customer Information Update Unit. The relevant Quick Guide and List of Economic Activity Codes can be downloaded using below link.
Quick Guide for How to change Taxpayer Profile Information
List of Economic Activity Codes