Hi
To solve your question, simply follow the following steps:
1. open the receipt you incorrectly created
2. duplicate the receipt
3. put negative sign in front of Received Value. e.g. if previously you put 1000 dollars for Received Value, now you put -1000 dollars for Received Value

Above steps will clear the 'On Account' Amount.

Now you can just allocate the amount to the correct customer.

Hope this answers your question.

Edwin
PM of HansaWorld