How can I make a payment through the portal if no invoice is available?

You can renew your active service through the portal without an invoice. Please refer to the payment guide at https://www.ipserverone.info/knowledge-base/how-to-renew-services-through-portal/, which applies only to services still active or within the renewal grace period. For domain services, this option is available only if the domain has not been expired for more than 40 days.