Hi there,
Thanks for reaching out to us here. QuickBooks offers a variety of features that help you streamline your accounting. I'll be happy to share info and steer you in the right direction.
In order to add GST to your estimates you'll have to set up sales tax on your account first. I encourage you to check out this article here that shows you how to set up sales tax. Once you've set up the taxes, you can then add it your estimate line items when creating it.
You're welcome to ask other questions. I'm here to steer you in the right direction.
