How to calculate Salex tax when tax basis is "Cash" (Not Accrual) and Credit Note is applied on Invoice?

How to calculate Salex tax when tax basis is "Cash" (Not Accrual) and Credit Note is applied on Invoice?

Hi Support,

I have created one invoice, Invoice has three item, each item price is $ 100 and tax is  $ 10 %.
Tax basis is "Cash" not accrual.
Credit Note is created on Item 1 with tax (10%) : $100 (Item Price) + $ 10 (Tax) = $ 110.

So invoice is as below

Name      Qty       Price      Tax      Amount
Item 1      1            100      10%      100     
Item 2      1            100      10%      100
Item 3      1            100      10%      100
================================
                                   Sub Total      300     
                                           Tax        30     
                                          Total      330
                           Payment Made      220
                        Credit Applied          110
===============================
                               Balance Due      0

Now When I looking the tax for this invoice in Tax Report page then it show me $20.01? I am not able to understood , how this is calculate , what is the formula and is it right or wrong?