Uniconta's misc. purchase charges function is used to allocate charges, such as freight, proportionally to all inventory items on an invoice and thereby increase their cost price on the balance sheet.
If, however the invoice that the user is adding a purchase charge to does not include any items that are set up in Unicontas Inventory module, then Uniconta cannot update the cost price of the items on the invoice. The user will then receive this error message.
If the posting instructions set up in your item group/vendor group are not set up with a balance sheet inventory account on which to increase the cost price, then you will also get this error.