For now, editing the tax payment isn't possible. You'll have to delete the payment first and record it with the correct amount. Let me guide you with the steps.
To delete the payment:
Click Taxes on the left menu.
Go to the Payments tab.
Select the payment.
Click the drop-down arrow beside the View hyperlink, then choose Delete.
5. Click Yes.
Once done, record the correct amount of the tax payment.