Multiple Invoices in one lockbox transmission?

Hi,

We are trying to utelize the lockbox functionality to upload receipts. We receive one daily amount from a third party which relates to multiple invoices that relate to multiple customers.

Our thought is to use lockbox to create receipts within the batch based upon invoice number rather than 1 customer. If the system is unable to identify the invoice number, it should create an unidentified receipt. The user would then go in and manually allocate to customer/invoice.

Question is - what format does transmission file need to follow to simply list invoice numbers rather than invoice and customer number. Do we still need to create multiple 'Payment' and 'Overflow Payment' identifiers within the file? Can we just have one payment with multiple overpayments identifiers and importantly leaving the customer number blank??