Yes, you can pay multiple invoices using a single transaction. Please follow the steps below.
Log in to Client Area
On the Home page, under Overdue Invoices, you will have the option to Pay Now to make the payment for all due invoices.
or Go to Billing >> My Invoices
You will get a button called Pay All in the top-left corner to pay all due invoices using a single transaction.
You will get a single combined invoice for all unpaid invoices. Select the payment gateway from the drop-down, click on the Make Payment button, and proceed with the payment.