The following variant applies only to sole proprietors.
First you must enter a private deposit in the cash book for the desired amount that the cash in advance should have (e.g. 300€).
The next step is done only during the cash closing.
In order to keep the cash on hand, you must make sure that this cash on hand is not transferred during the cash closing.
Therefore, before closing the cash book, you must enter a private withdrawal in the amount of the day's sales.
If the sales amount to e.g. 2384,47€, this amount is booked as withdrawal.
When closing the cash book itself, it is important to make sure that you set the amount in the bank transfer field to 0, so that the final balance contains the previously entered previous balance as the final amount, i.e. 300€.
After successfully closing the cash register, you can check the previous balance by clicking on "Close cash register" again.
In our example, it looks like this: