Good evening, @4lipssake.
QuickBooks adds up to 400 characters and 1000 characters in the Footer section in the invoice. Although, you can create an invoice by importing an MS Word file. You’ll be able to put the Terms and Conditions in the word file and upload it into the invoice.
Some customers have found this article helpful.
Import custom form styles for invoices or estimates
Let me know if there’s anything else I can help with. I hope you have a great week.