Quickbooks introduced a new & worse template for supplier and customer entry. The supplier template no longer has a place to enter the supplier VAT number.

We strive to provide the best product experience possible, Ecotao.

I understand how important it is for your company to enter the supplier's VAT number on the supplier's template. However, this option is unavailable in QuickBooks Online (QBO). We see consumer feedback as an opportunity to improve the numerous features of our products. I'd recommend giving our engineers direct feedback. They may look into this suggestion and incorporate it into future updates. Let me demonstrate:

1. Go to the Gear icon.
2. Hit Feedback.
3. Type in your recommendation in the Share your feedback field.
4. Click Next.
5. Follow the on-screen instructions to complete the process.

I've attached screenshots below for your reference:

Furthermore, you can visit his page to stay up to date on the latest software improvements and enhancements with QBO: Customer Feedback for QuickBooks Online. For now, you enter the number in the Memo box as a workaround. Here's how to enter them if you want to create a bill:

1. Click the + New button.
2. Select Bill.
3. Choose a supplier from the Supplier drop-down menu.
4. Enter the appropriate category, item, description, VAT rate, and amount.
5. In the Memo box, enter the supplier's VAT ID.
6. Click Save and close to complete the process.

Feel free to visit the Taxes page for more insights about managing your taxes in QuickBooks. 

Let me know in the comments below if you've got questions about VAT in QuickBooks. I'll be here to help you out. You have a good one.