Net GST = GST on sales (1A) − GST on purchases (1B). A positive figure is payable to the ATO; a negative figure is a refund. Accrual basis counts GST when invoices are issued and expenses are dated; cash basis counts GST only as invoices are paid (the received portion) and on expenses you've marked paid. Figures are a summary from your invoices and expenses — confirm against your records before lodging a BAS.