Income received March 2020, Refunded income June 2020. How do I make GST amendments to correct the BAS statement for March period?

Hi eo2, 

Typically when making changes to a prior BAS period the best way forward would be a Journal Entry. This would not change that account's balance, but would allow the changes to be picked up by the GST centre when you come to prepare your BAS, helping achieve the figures you are looking for.

You can see the steps to complete this below: 

1. Select the + New button and select Journal entry. Enter a date that falls in the BAS period you are preparing. 
2. On Line 1, enter the account you'll be using for an adjustment (if you have a clearing or adjustment account already set up, you can use this, or create a new one. Speak with your accountant if you are unsure on the account type you should use). Enter the amount you need to make the adjustment by, then select the tax code you need to adjust for. Enter a description for the journal.
3. On Line 2, enter the same account used for Line 1. Enter the same amount to balance the journal, and enter the tax code Out of Scope. Enter a description, then select Save.
    

This journal creates an 'amendment' that will then reflect in the totals of the BAS you are marking as lodged. However before saving, I would encourage you to reach out to your accountant or bookkeeper to ensure this work around supports your books. After completing the journal you can look through GST Exemption Report to find your newly created amendment showing, which can be found with these steps here.

While the journal entry method provided will 'amend' your totals and achieve the goal you are trying to attain, we are unable to advise what is best for your books as we are not accountants.  

Thanks, 

-Steven