- **G1 (total sales, GST-inclusive):** $110,000  
- **1A (GST on sales):** $10,000  
  - Working: $110,000 ÷ 11 = $10,000  

- **1B (GST on purchases):** $6,000  
  - Working: $66,000 ÷ 11 = $6,000  

- **W2 (amounts withheld from wages):** $8,000  
  - Working: $40,000 × 20% = $8,000  

- **Net amount payable to the ATO:** $12,000  
  - Working: ($10,000 − $6,000) + $8,000 = $12,000