How to categorize an income tax payment to the ATO?

Welcome to the Community, VietAu. 

We can create an expense account where we can allocate the income tax payment made to the ATO. Let me guide you how. 

1. On Accounting tab select Chart of Accounts.
2. Select New.
3. On Account Type, select Expenses.
4. On Detail Type, select Taxes Paid. 
5. Enter a Name of that account.
6. Select Save and Close. 

You can create an expense transaction or allocate the downloaded bank feed to the newly created account. 

Let me know if you have any other questions and I'd be glad to help.