Have you made purchases out-of-state or online?
If no sales tax was charged and collected, you probably owe Connecticut "use" tax on your purchases. Such purchases, no matter how falsely advertised, are not "tax free" even if the retailer fails to let you know you owe the tax they have refused to collect for you.
Some taxpayers are getting bills from DRS for past use tax on known purchases. The bills are real and so is the offer to settle by paying the tax and interest due without penalty. That offer is time limited before further collection efforts become necessary.
Every year, taxpayers are required to disclose untaxed purchases. File Form CT-1040 Schedule 4 and pay any use tax due when filing Connecticut income tax -- subject to civil and criminal liability for failure to do so.