A tab hides and unhides just like any other field on the form.
a) make sure the tab has a use equate
b) set the "Hide condition" for the tab. (Usually using the session value of some other field on the form. For example;
p_web.GSV('inv:paid') = true
c) on the parent field (inv:paid in this example), go to the client side tab and add the Tab's Equate to the "reset list".
Cheers
Bruce