You can directly reach out to customer support in QuickBooks Online. This way, they can discuss with you the refund process with regards to your sales tax charge in your subscription. Here's how you can connect with them:
Click the Help icon.
Hit the Contact Us button at the bottom.
Enter your concern in the description, then click Let's talk.
Select Get a callback.
Click the Help menu in the upper-right hand corner.
Type in "Talk to a human", then press Enter.
Look for I still need a human and click on it.
Click Contact Us.
Select between Send a message, Schedule an appointment, or Get a callback.
Just a heads up, due to COVID-19, we have limited staffing and have reduced our support hours to 6 AM-6 PM PT Monday-Friday. We will resume normal hours as soon as possible.To ensure we address your concern on time, check out our support hours.
In case you need help in performing other tasks in QuickBooks Online, you can check our articles here. Make sure that the topic is set as "QuickBooks Online."
Just tag my name in the comment section if you have any other concerns or questions. I'm always here to help. Stay safe.