Hi Antonio,

Let's perform some basic troubleshooting steps to isolate the behavior encountered in your QuickBooks Online account. To start with, use a new incognito window or a different supported browser. Using an incognito window does not store any data file.

Here's how:

• Google Chrome: press Ctrl + Shift + N
• Mozilla Firefox: press Ctrl + Shift + P
• Safari: press Command + Shift + N

Then, log in to qbo.intuit.com and attempt to create and save the transaction. Make sure in the Amounts are field you have set it to Exclusive or Inclusive of tax and in the GST column per line item, make sure you have selected a GST code as well.

If you were able to save the transaction in the incognito window, let's go back to your regular browser and clear cache and cookies on it. 

Feel free to post back in the Community if you have other QuickBooks concerns.