To adjust the security settings:
In the browser, choose the "Tools" menu and then "Internet options".
In the tab "Security" choose "Trusted websites" and the button "Websites".
First uncheck the following function at the bottom of the window: "Server verification (https:) required for all websites in this area".
Then type the following addresses into the input box: http://*.fgov.be, https://*.fgov.be and *.socialsecurity.be.
After each address, click on 'Add'.
On the same tab "Security" you also have to uncheck the "Enable secured mode" in Windows 7.
Close the various windows and your browser.
Start a new browser window and go to www.belcotaxonweb.be. Via "Access" (in the upper right corner) and "Login with electronic identity card" you can log on to the application "Belcotax" itself.
It is recommended not to use the possible shortcut on your desktop and to log in directly via www.belcotaxonweb.be.
In order to solve a possible problem with the eID middleware, you should download the latest version from http://eid.belgium.be under 'Installing the eID software' or http://eid.belgium.be/nl/je_eid_gebruiken/de_eid-middleware_installeren/.
Finally, it is in any case useful to delete the cookies, temporary internet files and browser history on PC or network level to make sure that all sessions with errors are removed, via the menu Extra > Internet Options > General tab > Delete browser history > Delete.