Jones Pty Ltd has a GST turnover of less than $10,000,000. Assume a monthly return is lodged and tax invoices are issued at the time of sales and purchases.

In July 2021, sales including GST were $11,000, while purchases including GST were $5,500. No moneys were received or paid.

In August 2021, sales including GST were $11,500, while purchases including GST were $6,050. No other money was received, but $5,500 was paid.

In September 2021, sales including GST were $13,200, while purchases including GST were $7,150. $11,000 was received, while $6,050 was paid in the month.

Required: Given the above information regarding three months of trading under the GST regime, what accounting method should they adopt?