Change the sales tax rates on future generated invoices. You may need to do this if your local government changes your sales tax rates.
Configure WHMCS to charge the required Goods and Services Tax (GST) on purchases and collect GST Identification Numbers (GSTINs) in India.
Configure WHMCS to charge the required Value-Added Tax (VAT) on purchases and collect VAT Identification Numbers (VAT IDs) in Europe.
Update WHMCS's tax configuration when sales tax rates change. Make sure to do this as close to midnight or the system cron run as possible.