In order to make a deduction or charge I must first make  a price list from the settings.

In this example I make a charge as a price list  in the pricelist settings and then set the rate of the charge/deduction from the categories pricelist.

Then I have to make a product with a Product handle the name of the charge, add a description, the measurement unit  has to be addoon and  put a category.

Next step is to go to Purchases / Sales and make a document with a product or service.Then I right click inside document  to open the menu and select Calculations, select the charge I want and then the create button.