On the References tab, select
Update Table.
Select one of the following:
- Update page numbers only This only updates the pages that the headings are on, and ignores any changes to the heading text.
- Update entire table This will reflect any updates to the heading text, as well as any page changes.
Select OK.
Note
Manually created tables (not created automatically from the headings), can't be updated by Word. You'll need to manually type your changes in the table of contents.