How can i allocate the correct tax to a supplier when I enter an expense

Hi there, 

QuickBooks makes it hassle-free for you to record your expenses, letting you enter them when they occur. You can also edit or delete expenses you recorded to make sure everything is accurate. I'll show you how. 

1.     Select the + New button.
2.     Select Expense.
3.     In the Payee field, specify a supplier. You can specify the name of a person or a business. If your transaction covers multiple petty cash expenses, leave this field empty.
4.     Select the Payment account to which to credit this expense.
5.     Enter the date of purchase in the Payment date field and specify the Payment method for the expense.
6.     (Optional) You can use the Ref no. field to enter an identifying number from the purchase receipt. (Note: QuickBooks Online Plus users: When location or class tracking are turned on, additional fields for Location or Class appear. You can turn on location or class tracking features in Account and Settings on the Advanced tab).
7.     (Optional) Enter a description of the expense.
8.     Enter the amount of the purchase and any Tax paid (if applicable).
9.     Select Save and close or Save and new.   

I'll attach a screenshot for reference:

Let me know if you have other questions. I'll be on standby. :)