Hello there, @Ralphthefluffycat.

I can guide you on how to fix the negative amount on your payable account.

The negative amount will show on the sales tax liability once you make an overpayment in QuickBooks. As you make sales, the sales tax collected reduces that negative amount until it gets to zero. Then, it will start showing a positive amount.

If you want to clear the negative amount in the sales tax payable, you can enter a positive adjustment. You can check this article for detailed steps on how to adjust Sales Tax Liability in QuickBooks Online.

Also, I'd suggest consulting an accountant for specific suggestions on how to adjust the sales tax liability in QuickBooks. 

For additional tips, while managing your transactions and sales taxes, you can as well open this article: Sales tax in QuickBooks Online.

I'm always here to help if you have any other questions. Just add a comment below. Wishing you a good one!