I'm not sure this is what you're asking for, but IIG has a pretty good deposit enhancement. It lets you process and post multiple payments against invoices and sales orders. A couple of nice features is that is 'posts' deposits against sales order orders (not just invoices) to AR and the GL and will let you apply prepayments and credits against invoices in invoice data entry. http://www.iigservices.com/ebiz/pdf_enhancements/CCP_Credit_Card_Processing_510.pdf