Company vat number not reflecting on invoice header , although it has been inserted on company profile.

By default, the company's VAT aren't actually shown in the invoices in QBO, Venessa.

You might want to create a custom field in your sales template where you can add this info. Here's how: 

1. Go to the Account and Settings, then look for Custom Form Styles.
2. Look for invoice template that you're using. If you haven't set up anything yet, you'll see a Standard template.
3. Click the Edit link under the Action column. 
4. Proceed to the Content tab. Then, click the header section of the invoice to see the list of fields that can be customized.
5. Scroll-down to Display section and click Custom field.
6. Add a custom field for the VAT number. 
7. Click Done. 

Let me also share these articles to add more info about customizing sales form: 

• How to add custom fields to invoices
• Customize your invoices, estimates, and sales receipts in QuickBooks Online

Please click the Add a reply button if you have follow-up questions. I'll get back here and offer my help again.