Thanks for dropping by here in the Community, @useruday. I'll share some information about your query along with the workaround.
Currently, the option to create an additional address for the same client in QuickBooks Online is unavailable. The reason for this is that GST is a location-based tax. You'll need a separate client profile for different GST Numbers but the same client. As a workaround, you can consider setting up a new client profile and then adding a unique character to it. Here's an example: Karen McCartney (O) - Old address | Karen McCartney (N) - New Address.
You can refer to this article for more information about how to add and manage customers in QuickBooks Online.
Additionally, I'll be leaving these articles to help you in the future:
Feel free to notify me by clicking the REPLY button below if you have other QuickBooks-related questions. I'll be more than happy to provide additional assistance. Keep safe and enjoy the rest of the week!
