Thank you for following up with us here on the Community page, @dcaroli.

I've read your original post, and I'm stepping in for a moment to share with you some insights about setting up taxes for expense transactions.

Usually, the option to set a tax for purchases and to set the default tax rate selection from the Accounts and Settings is available for QuickBooks Online (QBO) International. If you're subscribed to any of the international versions of QuickBooks, please make sure to select the desired code so bills will compute the accurate taxe/s.

1. Select Bills from the (+) New icon.
2. Input the details, then select the correct tax rate under the Tax column.

If you had the US version of QuickBooks, you only have the option to set up taxes for your sales transactions and not with purchases. As a workaround, you can either create an expense account or a service/non-inventory item and add it to your bills for the amount of taxes.

Here's how to add an account from your chart of accounts:

1. Go to the Gear icon, then select Chart of Accounts.
2. Select New to create a new account.
3. In the Account Type dropdown, choose an account type (Expense).
4. In the Detail Type dropdown, select the detail type that best fits the transactions you want to track. 
5. Enter the account's name, and fill in the necessary information.
6. When you're done, select Save and Close.

And, here's how you can add a service item to QuickBooks Online.

To know more about setting up taxes for QBO US and International, I recommend opening these links:

• Sales tax in QuickBooks Online US
• How do I set up sales GST/VAT rates and use them on forms? (International QBO)

I'm also adding these screenshots for your visual references.

Please let me know how else I can help you with recording your transactions and taxes. I'm more than happy to help. Have a good one!