Debt has interest, liability in payable doesn't has interest. So they are totally different. The new receivable could be used to pay for the past payable liability. If the total of new receivable is greater than the payable, then the extra will add up to the cash balance, and this is the benefit that Groupon has been enjoying for the past 3 years.
With over $1 Billion cash ( free interest) Groupon can invest in Credit Card for example. Let say 20% annual return, within 5 years this $1 Billion will become $2 Billion, inwhich $1Billion will become Groupon Cash that can be add to balance sheet.