40A(3) is applicabe only in respect of an exp which is excess of Rs. 20K. therefore if an assessee makes payment over 20k for two different bills (none exceeding 20k) at the same time in cash/bearer cheque 40A(3) is not applicable. If the payment is made to same person more than 20k in a day sec 40A(3) is appliacable.
Some exception are there. They are covered under rule 6DD.