Tax collected at the time of sale = Rs 1,22,500
Tax collected at the time of purchase = Rs 1,00,500
∴ GST payable = Tax collected at the time of sale − Tax collected at the time of purchase = Rs 1,22,500 − Rs 1,00,500 = Rs 22,000
Thus, the GST payable by Chetana Stores is Rs 22,000.