AvaRates Now: Avalara's Free Sales Tax Rate Calculator Existing Users New Users Email: Password: Remember me on this computer. Forgot your password? To use our free sales tax calculator you must have an Avalara.com account. To register, click the Sign Up button below. Back to top Download and install AvaRates Now by clicking the button below. It will place a shortcut to AvaRates Now on your desktop and Programs menu.