Hello,

firstly you should book the receipt in different way. By two lines:
first line, select the invoice 10720.51
second line, book the prepayment 1.234.46

Also please check settings in Sales orders>>settings>>Down Payments Untick " Use sales Order. No for prepayments.
And Tick in Sales ledger>>settings>> Account usage S/L >> "Use prepayments, not on Account" and force Unique prepayment numbers"


Best regards,

Hansaworld support