You can add more complex tax on your forms by using custom pricing rules to modify the form total depending on the answers to certain questions.
For example, we might add a 10% tax if the billing country is Australia, where 100% (original price) + 10% (tax) equals 110%, or 1.1 in decimal form, which is what we multiply the form's total by in the rule.
Add any other required pricing rules.
For example, we might want to add a 20% tax if the billing country is instead the United Kingdom.
You can also set a label to describe the custom pricing rule in the checkout.
You may only use a single label for adjustments made by all rules combined.