List numbering in Microsoft Word is downright strange! In effect, you set up a palette of numbering styles and then choose which one to use. If you want all your Heading 1 text to be numbered, for example, then you edit the Heading 1 style and change the numbering style associated with it. So far, so good.

However, suppose you wish to have nested numbering styles as follows:

1. This is a main heading
  1.1 This is a sub-heading
  1.2 This is another sub-heading
    1.2.1 This is a sub-sub heading
2. This is the next main heading

You want all your Heading 3 text to have the format a.b.c so you go to change the style of Heading 3. Wrong! Although you can change the flat numbering style, there’s no option for setting up multi-level numbering.

Instead, multi-level numbering lives in a hive of its own. Rather than assigning numbering styles to paragraph styles, as you do for simple flat numbering, you must assign paragraph styles to multi-level numbering styles. In Word 2007, you’ll find the multi-level list options on the Home tab:

The options here are fairly self-explanatory, and are explained in detail in my book Microsoft Office Word 2007 Essential Reference for Power Users. The key point to understand is that if you want your headings to use multi-level numbering, you can’t do it by changing the heading style; instead, you must pick or create the numbering scheme and then tell it which styles to pick up.

Multi-level numbering: 1, 1, 1, ...

I had a recent problem with a Word 2003 document in which the headers were picking up the following numbers:

5. This is a main heading
  5.1 This is a sub-heading
    1.1.1 This is a sub-sub heading
    1.1.2 This is another sub-sub heading
  5.2 This is the next sub-heading

It seemed that whatever I did, the Heading 3 style refused to acknowledge the higher level numbering, even though it was set to restart with each Level 2 heading.

As I discovered, you need to approach this sort of problem top-down instead of bottom-up. Ignore the problematic Heading 3 and instead select one of the main headings (i.e. Heading 1). Then modify the multi-level numbering style that Heading 1 is using so it picks up Heading 3 – in the case if my document, the numbering had originally been set up only with Heading 1 and Heading 2 defined.

And, hey presto! The numbers started to behave themselves:

5. This is a main heading
  5.1 This is a sub-heading
    5.1.1 This is a sub-sub heading
    5.1.2 This is another sub-sub heading
  5.2 This is the next sub-heading