Change the sales tax rates on future generated invoices. You may need to do this if your local government changes your sales tax rates.
Change the system default currency from USD to another currency. Only do this if there are no invoices or transaction data in WHMCS.
Change the default order form template. The system uses order form templates when it displays products, the shopping cart, and checkout.
Change the default product group that displays to customers. The default group displays at the top of the Admin Area list of products.
You can change the From address that your WHMCS installation uses when sending email.
The system character set determines how WHMCS handles many special characters. If you alter this value in your WHMCS configuration, you must also save the relevant language files again using the new character set.
The system theme controls the appearance of the Client Area and your online store.