In SBO2005A there was a problem with the open balance BP concerning the next situation
create an in- or outgoing payment by
1. select the customer/vendor
2. Select an invoice (example invoice 100 EUR)
3. go to moneybag and enter an amount of 99 EUR
4. Try to save the payment.
5. system will give you a message the amount to be paid is not equals the invoice SAVE payment
So far so good.
Now when you save the invoice also in SBO2007A you will save the invoice with reference to that payment and the mark: payment on account will be active. the only improvement from SBO2005A and SBO2007A is that at least the balance is correct ( this scenario is one of the fixes when upgrade to sbo2007A reconciliation errors).
In my opinion this is wrong behavior. One way or the other. A payment is with reference to an invoice and then it would be in this case a partial payment or the payment is on account and then there should be no reference to that invoice.
In my opinion the correct behavior must be after saving the payment: error message: please create a partial payment or select payment on account because selected amount and payment amount are not equal.