An important rule known as the "mailbox rule" says that an acceptance is effective once it is put in the mailbox. Purchase agreements often include contingencies or situations where you can withdraw from the contract without penalty.Having an offer accepted does not force you to close. You can withdraw your offer in many cases up to the closing date. The ASIS contract verbiage to cancel a contract at their sole discretion can be used to get out of a deal without consequences. A clause in a purchase agreement that gives buyers and sellers the right to cancel a contract if certain terms aren't met. Legal Implications: If certain conditions aren't met, the contract can be canceled.