Tipalti - Tipalti is a supplier payments automation solution to streamline all phases of the AP and payment management workflow.
Bill.com - Bill.com provides ACH payments processing, automates your accounts payable and accounts receivable processes.
PayStand - PayStand is a payment & eCommerce checkout system
BillGrid.com - BillGrid is an easy to use online invoicing, billing and expense management system that will save you time with tracking clients projects, expenses, invoices and payments.
nvoicepay - payment mass payment
ChargeOver - ChargeOver automates recurring billing, subscription billing, & payment acceptance. A SaaS that integrates with Xero, Quickbooks, & has an API. Free trial.