Hi 2167269albertalt,
Welcome to Community! It's essential that your GST number is entered to ensure accuracy in reports, remittances and other areas of your books. QuickBooks Online enables you to manage your taxes effortlessly. I'd be happy to help!
Follow these steps to edit your GST number;
1. Open Taxes, then Sales tax, from the left menu
2. Click on Manage sales tax
3. Select Edit agency settings for the appropriate sales tax agency
4. Make the necessary changes to your GST/HST number
5. Review the other fields and make any changes as you see necessary
6. When finished, hit Save
Please don't hesitate to reach back out with other questions. We'd be glad to assist!