Death of proprietor

Dear Sir, One of my friend expired recently. He was running a good business. As of now, there are debtors as well as creditors in his books. His father (as his legal heir) went to the bank and explained the situation that they will receive payments from debtors and they also have to pay off creditors. So Bank informed him that they can receive money in his account but they cannot write cheque and make payments as legal heir. Bank informed his father that he will have to pay off creditors from his personal (father's) bank account. But then how will we show all those payments in his income tax return? Should we follow bank's advice? How shall we make payments to creditors? Please guide.