write checks one can't cash

A check (or "cheque" in British English) is a document that orders a financial institution to pay a specific amount of money. The money would be taken from the account of the person who wrote the check and paid to the person in whose name the check has been issued. If one writes a check for an amount of money one does not have available in the associated account, also known as writing a bad check, the resulting check cannot be cashed by the receiving party. In this situation, a promise of payment was made by writing the check, but the promise is not honored due to insufficient funds.

• "You're acting like a frat boy, which is fun and all, but you're writing checks you can't cash."
• "“I think your mouth might be writing checks you can't cash.”"

• overpromise
• put one's money where one's mouth is