Web: Yes. You can also make a payment to a single account or partial payments to all accounts by clicking on the Billing & Payments button. It will allow you to check the accounts to be paid and change the amount for each account by clicking on Other Amount. After entering the amounts to be paid, click the Pay Now button.
App: Tap the Bill & Pay gadget. If paying the total amount due, tap the Pay button. If paying a partial payment, tap the Pay Partial Amount, tap on the account and adjust the Pay Amount.