Hi @david3 please also see this thread. Some of the notices are legit. For the CP53E notices we'd recommending looking at this from the IRS: Understanding your CP53E notice

From the IRS website regarding QR codes: "Many notices have QR codes that help direct taxpayers to their online tax accounts. In addition, these letters inform the taxpayer of the status of their unpaid balance, options for resolution and their rights in the collection process."  

However, when in doubt, always verify notices by going directly to IRS.gov/Account instead of scanning the QR code.