I'm here to share some information about VAT, kamonwan.
Once we turned on VAT, we're unable to turn it off however, we can modify the default settings to No VAT. This way, you'll not be prompted to enter a VAT code. Let me guide you how:
From the Gear icon, select Account and settings.
Go to the Advanced tab.
Click the Accounting section.
Change the Default tax rate selection to No VAT.
Click Save and then Done.
I've added these articles that share about VAT rates: