Can your bank account be closed if you've had the account for 6 months and you've just been reported on the Chex Systems?

possible. After my five years with chex systems passed, I opened a checking account and the bank closed it after two months due to my chex systems record. They froze it and then closed it without notice to me. I found out when the ATM card quit working. I then had to get Chex systems to write a letter to them because my record should have been gone after five years, but that did not help me get my account back.

Yes, if the account holder resides in a state where the banking laws allow the action without due process of law.