Sometimes it's hard to use the MS Word Bookmark feature to put Anchors (Bookmarks) just before the Heading of "TOC" or just before the Heading of your "start" (or "Beginning"), especially, if that Heading has a "page break before" attribute.
If you have inserted Guide Anchors (or Bookmarks) using Word, and later find that the Guides don't work, this may be the reason:
When the HTML file is saved, the software will try to consolidate tags where it can... so sometimes it will put your Bookmark inside another tag... where it won't work..
To fix it, save your Word file as HTML, filtered. Then open the HTML file with a plain text editor, such as Notepad, and move the Bookmark tag away from the other tag that has it captured.
For "Table of Contents" Guide Anchors (which you placed earlier):
Search for your table of contents title, find <a name="toc"> , and move to just before the title.
For the "start" Guide, search for the first Chapter Heading name (or whever you want to call the "start" (only you, the Author, knows what that is), find <a name="start">, and move it to just before the Topic Title or Chapter Heading... or what ever you decide is the best place to have your reader start.
To read how to insert the Anchors (Word Bookmarks) into your MS Word file, go here:
Anchors for Table of Contents (TOC) and Beginning (start) of file in MS Word