WHY DO I GET THIS ERROR MSSG WHEN TRYING TO ADD TRANSACTIONS TO MY BANK? One or more charge lines do not have a tax code associated with it.

Thanks for posting here, @marshaparchment,

Allow me to share some insights about this error you're getting in QuickBooks Banking and how you an resolve it.

The mentioned error normally comes up when adding an online banking transaction that doesn't have a tax code in it. To avoid this from happening, make sure to input all necessary information to add bank entries successfully. 

See this:

Another option to resolve this error is to create a counterpart transaction in QuickBooks then match it with the bank entry. Do that by going to the + New icon the choose the sales or expense transactions you can match in the Banking page.

Once done, use the Find match option to link the two transaction not the Add or Categorise radio button. See this link to learn more about matching bank entries in QuickBooks: Categorise and match online bank transactions in QuickBooks Online

Let me know the result after trying out the steps. I'll be right here to help you further, just tag me on your reply. Have a good one!