Hi info-qualitycont,
Welcome to QuickBooks Community! QuickBooks Online makes it easy for you to ensure business information is properly displayed on your company forms. I'd be glad to assist!
Here's how to include your HST number on your invoices;
1. Open Taxes from the left menu and select the Sales tax tab
2. Click on Manage sales tax
3. Hit Edit agency settings to the far right of the associated agency
4. Enter your GST/HST number, when the Next period starts, your Filing frequency and your Reporting method
5. Hit Save
You're all set! The information will now appear on your invoices.
If you have any other questions, please don't hesitate to reach out again. We're always happy to help!