One customer paying other customer's invoices

I have a situation where one customer will pay for several other customers sales invoices. This arises because my product is a medicine (which is an inventory item(s)) and each customer must have a detailed invoice stating exactly what they have been sold so the items cannot be combined in a single invoice. When I see families the parents pay for the child At the moment I am using receive money into the bank account from each individual customer in the group in the normal way . If the payment is an EFT payment this causes problems when it comes to reconciling the bank statement. The customer transfers one single EFT payment to cover all the invoices but when the bank statement is imported all the sales invoices show up (as expected) causing the balance of the bank account to be inflated by the amount of the seperate invoices + the EFT payment. For example in the bank account window it would show up like this
Receive Money (Mother invoice) $10
Receive Money (Child 1 invoice) $5
Receive Money (Child 2 invoice) $5
Receive Money (EFT payment from imported statement) $20
Result: double amount shown recorded in bank balance.
One possibility would be to get the customer to transfer or pay each invoice seperately but I wish to avoid that .
Is there something I have missed or can anyone think of a work around to handle this situation?

I don’t really understand what’s the issue.

You receive $20… then allocate this $20 to multiple invoices.

See: Guides | Manager

Hi Lubos,
The method in the link does not seem to work . Entering all the data as instructed produced a payment of $0.00 . On selecting the sales invoice in the correct field the amount column remained blank . This was repeated for any subsequent invoice added using the add line button. See attached screen shot. Is this expected behaviour?
I tried the same method with the same initial invoice in the sales invoices → view → recieve money → receive in → receipt . There the amount was filled correctly but any other subsequent invoice the amount remained blank. See screenshot2 This I imagine is expectected behaviour but I add it to show that the invoice in question functions correctly in other parts of the app. Just to reiterate the invoices are from different customers to be paid by one single customer.
Manager 14.10.6 running on Ubuntu 12.04 LTS
Thanks for your help.

You need to enter amounts manually. That is specify, how much you want to allocate to each invoice.

Thanks lubos . All good.