Spending on debit cards is catching up with spending on credit cards and, given current relative growth rates, will overtake credit cards within the next couple of years.According to the latest Reserve Bank payment data, consumers made 190 million purchases on their credit and charge cards in September, worth a total of A$24.8 billion.That is an average of 11.8 purchases on each of 16.2 million accounts, worth $129.80 per transaction.On their debit cards, consumers made 364.2 million purchases in September, worth a total of $19.4 billion.That is an average of 8.8 purchases on each of 41 million accounts, worth $53.26 per transaction.Over the 12 months to September the number of credit and charge card purchases per month rose by 5.7 per cent and the average number of purchases per account rose by 1.9 per cent. The value of purchases rose by 3.2 per cent.On debit cards, over the same period the number of purchases per month rose by 12.9 per cent and the average number of purchases per account rose by 7.8 per cent. The value of purchases rose by 9.5 per cent.The value of debit card purchases is growing at three times the rate of growth in credit card purchases.