If you are in the process of creating a listing and want to check if the data you have entered is valid, you can do so by clicking on “Check item”. The item will then be checked by ebay, but not uploaded yet. If you want to turn this function off or on, then open the settings and switch to the tab “Listing” in the left navigation bar.
Change your setting in the upper right area by setting the checkbox. Confirm your changes by clicking on “Save changes”.