A person with a bank account writes a bad check (also known as a non-sufficient funds or NSF check) when he deliberately or with knowledge writes a check for an amount of funds he knows are not available in the account. The crime of writing a bad check may also occur when a person writes a check on an account that has been closed. Another bad check scheme that may result in criminal charges occurs when an account holder writes a check for an amount in excess of the funds in the account, and deposits the check in a second account (often at a different bank)—and then withdraws the funds from the second account before the check is presented to the first bank for payment.

Bad check laws vary from state to state, and are usually located in the state’s penal or criminal code (statutes). Banks and criminal prosecutors recognize that a person can inadvertently write a check for more than the funds on deposit in their account, and not every instance will result in criminal charges. But many state laws have an expansive definition of the required knowledge or deliberate intent to write a bad check, and a criminal prosecutor does not have to prove a defendant charged with a bad check offense knew exactly how much money was in the account when the defendant wrote the check to prove the defendant knew he was writing a bad check or deliberately wrote a bad check.

In Colorado, writing a bad check, also known as issuing a check with non-sufficient funds (NSF), is addressed under the state's criminal statutes. Specifically, Colorado Revised Statutes section 18-5-205 details the offense of fraud by check. It is considered a crime when a person, with the intent to defraud, issues a check knowing that they have insufficient funds in their account, or if the account has been closed. The severity of the charge can range from a petty offense to a felony, depending on the amount of the check and other circumstances. The law also covers situations where an individual writes a check from one account and deposits it into another, attempting to withdraw the funds before the check clears. While accidental overdrafts may not lead to criminal charges, the state's definition of intent is broad enough that a prosecutor does not need to prove the exact balance in the account at the time the check was written, only that the issuer knew the funds were insufficient. Repeat offenses or larger amounts can lead to more serious charges. It is important for individuals to manage their bank accounts responsibly to avoid potential legal consequences.