The Word default TOC only have three heading levels.You may need more. When inserting the TOC, choose Custom Table of Contents to specify formatting—including how tab leaders and page numbers are formatted, and which heading levels to include.
If you formatted your headings with distinct styles for each level, but used styles other than the built-in heading styles, click the Options button in the Table of Contents dialog box to map the styles you used to the ToC framework.
If you want to change the font, font size, or other formatting attributes of the TOC, click the Modify button in the Table of Contents dialog box and specify your formatting for each TOC heading level. Any formatting you apply directly to the TOC is discarded whenever the TOC is updated.
Whenever you have made changes to your document, page numbers and headings may change, which will make your TOC incorrect. To update your Table of Contents, right-click in the table and choose Update Field, or choose Update Table from the Table of Contents group on the References tab. Select entire table or page numbers only and click OK to regenerate the table of contents from your headings.
Note: You don’t need to wait until your document is finished to insert a table of contents. If you’re creating a long document,create a table of contents from an outline so that you can navigate using the TOC while you’re working on the document.