Were sorry, QuickBooks encountered an error while calculating tax. Try reselecting the tax rate or reentering the product/service item and saving the form again

Hi hanlonbookkeepin,

Welcome to QuickBooks Community!  It's important that you're able to add your transactions from Square to QuickBooks Online seamlessly.  However, we are aware of the message you're receiving and our Development Team is currently investigating the unexpected behavior.  I suggest contacting us outside of Community, so we can take the necessary steps to provide you with an email notification when the issue has been resolved.

Schedule a Callback or start a Chat: click (?) Help in the upper right in QuickBooks Online > enter "Contact support" > hit Contact Us > provide a brief summary of your situation > hit Let's Talk > choose Get a callback or Start a Chat.
Social Media: Facebook, Twitter, and Instagram.
Support hours are from Monday to Friday between 9 a.m. and 8 p.m. ET.
 

If you have any other questions, feel free to reach back out.  We're always happy to help!