If you have been issued an account credit, you can apply this credit to any invoice you choose. Account credit will not automatically be applied to an invoice, as some customers in the past have complained about not having full control. Therefore, when you have account credit, even if it is enough to cover the whole amount of an invoice, it will not be automatically applied. Instead, you will need to login to your account, navigate to the unpaid invoice you would like to apply credit to, and then use the "Apply Credit" box that appears. Please see the attached image for an example, or contact us via live chat, phone or helpdesk for additional assistance.