Hello there, @Bellagamba.
Allow me to share some information on how spell-checker on QuickBooks Desktop (QBDT) for Mac.
By default, spelling is checked automatically no matter which language you're using on your Mac. With that being said, the option to turn it on is currently unavailable.
With this, I'd recommend reinstalling QBDT for Mac. This will fix any issues with the software and restore the spell checker to its normal functioning.
Feel free to visit this article to be more guided on the processes in QBDT for Mac: QuickBooks Mac User Guide.
Keep your post coming if you've got additional questions about the spell-checker in QBDT for Mac. I'll be right here to assist you further. Take care.
