Stop HTML stripping please

Hi Folks, I know this has been asked but I cant seem to get a straight answer. How do I STOP WP stripping my HTML. Yes I know, only use the HTML editor – but it still strips tags and its for a client who still needs access to visual. The Lists, divs etc disappear as soon as the WP parser runs. I tried the TinyMCE plugin and it works but doesnt include all other HTML that is sometimes needed eg UL’s, DIVS etc.
Is there a fix, plugin anything – I really need this for a client.
Is there a way to escape this in functions.php ?
Thanks heaps for any assistance.