Is recording my customer’s billing or shipping address mandatory on the payment page for tax calculation?

Yes, recording your customer’s billing or shipping address is mandatory as the tax calculation is done based on these two locations.

If it’s an intrastate transaction, your configured CGST + SGST settings will be applied on the amount and for an interstate transaction, your respective IGST settings will be auto-applied. This is applicable only for users in the India edition of Zoho Checkout.