My VAT number do not show on invoice?

Welcome to the Community, @manoloengineering. To make your VAT number show on the invoice, you need to set up your VAT in the Tax tab first.
 

Go to All apps > Tax > Set up VAT. After that, you need to fill in the necessary fields, and then enter your VAT Registration No. Once completed, click Next, then OK.
 

Once done, it should appear on the invoice after you select the correct VAT in the field.

You can visit this article for further guidance on using VAT: Set up and use VAT in QuickBooks Online.

For any additional questions, click the Reply button below.