You will use the deposit and deducted deposit function when you take deposits for goods/services that the customer has ordered (usually e.g. 10% of the value of the goods).
In the Storyous system, create a sales product with a name such as Deposit, VAT according to the rate of the goods/service (usually 23%), and if needed you can also use the "always ask for price" option so that the product is flexible for posting different deposit amounts. You issue a standard receipt and “sell” the deposit. (You do not set the sale of the deposit as a Deducted deposit).
Then, when charging the full amount of the product/service, you proceed as usual: post the product/service at the full price and then use the Deducted deposit product, which you create in the Back Office with a negative value (as shown in the image) and in the product settings change the item type to Deducted deposit.
The customer then pays the difference between the deposit already paid and the product price. A negative item cannot be set as variable, so it is best to use the amount -1 €, which you can post as many times as needed to match the paid deposit.