Formatting applied directly to a heading, that is, without modifying the underlying heading style, will be reflected in the TOC entry.

Font formatting that acts as a toggle (bold/not bold is one example) you may get seemingly unpredictable results. For example, if the heading is formatted as bold and you have turned that off by selecting the text and clearing the bold attribute, the TOC entry may appear as bold.

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Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional

Thank you both for the response. I have now updated the TOC styles too, but I also think that I was being affected by the issue of what was in the text being picked up by TOC. I think it has been resolved now on this document. I will take it forward to the next and hopefully it won't reappear! Thanks again.

Nick