I'm glad you've reached out to QuickBooks Community. I'm here to help provide some insights about the negative amount in the sales tax liability.
The negative will show on the sales tax liability once you make an overpayment in QuickBooks. You can view all the transaction to check if you made an overpayment. If there is, you'll need to clear the negative amount in the sales tax payable by adjusting the sales tax liability.
You can check this article for the detailed steps on how to adjust Sales Tax Liability in QuickBooks Online.
To further assist you with the steps, I recommend calling our QuickBooks Online Support Team. They have the tools to pull up to a remote session and walk you through the steps.
Here's how you can contact our phone support:
Please know that I'm just a post away if you have any other questions about the sales tax payable. Have a good one.