If there is a data entry problem on a page, the tab(s) to the right of the tab with the data entry problem will be disabled or disappear. For example, in the image below, a data entry problem exists on the Retirement Income tab and the normal Calculations tab is not displayed on screen:
To determine what the data entry problem is, select the last available tab (the tab farthest right that is enabled). There will be a "View Error Messages" button at the top-right of the page.
A message will be displayed about the problem with the data on the current tab.