Auxiliary items are extra items that your property sells to the guest.
You need to click the Engine Button for 'Settings' and go to 'Auxiliary Items'
First, you have to make the category for list items that you sell. Example Category types would be Mini-bar or Laundry.
Click 'Add new' and type the category. Don't forget to click 'Save changes'.
After you make category, you need to add new items and prices in 'Auxiliary List'.
If you want, you can add 'Sales Tax' for your aux items and choose the type of the tax, is it Exclusive or Inclusive. For 'Returnable', enabling this option will let you create items that you take a deposit for until they are returned. This deposit will be added to the guest's bill until it is marked as "Returned" at which point it will be deducted from the reservation balance. Last thing, don't forget to click 'Save changes' again.
You can click here to know more about how to add these auxiliary items to guest's bill.