A Software As A System (SAAS)-based system is disclosed herein for sending bills and payments in conjunction with a third-party accounting system. The system deploys a downloadable program interface to configure the third-party accounting system and then send and receive data between the two systems. The transmitted bills may contain an electronic signature, a line item billing, and/or other transaction-specific meta data, and, based on cash flow needs and outstanding bills, some or all customers may be offered a very substantial time-limited discount for immediate payment. Also, customers may use the line-item billing feature to withhold partial payments for specific issues attributed to specific items. Alternatively, a communication module between SAAS units (CSU) may be deployed to configure the third-party accounting system and then send and receive data between the two systems.