Remove tabs (pages) from form

don't even touch the pages propertybefore you move the fields around.

Say you have General, Foreign Trade, Item Tracking (Not looking at NAV right now) and you want to remove the Foreign Trade tab.

Here is a step by step approach:
1: remove the fields from the Foreign Trade tab

2: Move all fields from the Item Tracking tab to the Foreign Trade Tab, so that the Item Tracking tab is empty. If you have more tabs behind that, you have to move all fields for each tab to the empty tab on the left. Don't worry that they are on the wrong tab now, you will fix this in the next step

3: click the empty space in the upper right corner of the tab control, right where a new tab would go. This should select the tab control

4: open the properties page and browse to the Pages property. NOW you can remove the Foreign Trade from the tabs.

5: close the properties page, save the form, close the form, open the form. Your fields should now all be on the right tabs, and the Foreign Trade tab should be gone

source:
how to remove tabs in a tabular form