As with all WebPay payments, you control the payment amount and payment date.  You can set up an automatic payment for an E-bill by clicking on "Manage My Bills."  To do so, select the biller you wish to add an automatic payment to.  Click on the radio button next to "Add an automatic payment."  Once you have filled out the appropriate information, click on "Save Changes."  If you wish to pay an E-bill manually, click on the E-due icon located next to the biller within your "Payment Center."