Q: I bought something by check or credit card at a store that does not allow returns. Can I "cancel" the sale by stopping the check or instructing the credit card company to refuse payment?

A: If you already took the item, the transaction is finalized. You are not able to retract the sale. If you have not paid yet, you owe the seller payment. To stop the check or refuse payment is tantamount to refusing to pay what you owe, and is not allowed (C.M. 198:1).

If you did not receive the item yet, we learned that the Sages granted the legal ability to retract the item is taken, although they imposed a curse upon one who does so. A check or credit card should be no stronger than cash payment. However, in a typical commercial setting nowadays, signing a formal order form or paying in the routine manner is considered an act of kinyan situmta if the common business practice is to consider such transactions as final. [It is illegal to stop a check or cancel credit card payment after the item has been shipped.]