Note: Uninstalling the component using the Joomla extension manager or the Wordpress plugin manager does not delete the nBill database tables (this is so that you can upgrade, downgrade, or re-install without losing your data). If you want to permanently and completely remove nBill from your site, go to Configuration­->Global Configuration (on the nBill menu), select the 'advanced' tab, then click on the 'Delete Tables' button. See figures 1.9 and 1.10  DO NOT DO THIS IF YOU WANT TO UPGRADE TO THE LATEST VERSION AND KEEP ALL OF YOUR DATA.

Figure 1.9 - Accessing the global configuration page

Figure 1.10 - Deleting the nBill Tables

This will permanently delete all nBill tables from your database, and all of your billing data will be lost. In Joomla! you can uninstall using the extension manager. In Wordpress, you can uninstall by deactivating the plugin from the plugins list, then click the link provided to delete the plugin files.