Is there a way to change TIN to VAT No on the sales invoice.

Good day, nour.farouki@gma.

You have me to help you modify the registration number. Here's how:

1. From the Gear icon, select Account and settings.
2. Click the Company section.
3. Under Contact info section edit the address and add your company TIN number.
4. Click Save and then Done.

I've also added this reference for more information about setting up taxes:  How do I set up sales GST/VAT rates and use them on forms? (International QBO).

Let me know if there's anything else you need help with. I'll be around to assist you every step of the way.