Business interests in unlisted companies - IHT412 and IHT413

[dominoman]

My late father owned shares in many small unlisted businesses, often startups. I have listed them all out on form IHT412 (and used an extra Excel sheet too as there weren't enough rows on the form). Most attract Business Relief or Replacement Business Relief because he had held them more than 2 years.

I'm unclear if I also need to complete form IHT413 for each of these companies?

The IHT guidance notes state that I must fill in schedule 413 if the deceased owned a business or part of a business. But it also states that for Business Relief on shares use IHT412 and not IHT413. I'm confused because surely if you own a part of a business that is shares in the business.

Do I need to fill in IHT413 for each business he had shares in if I'm claiming Business Relief?

Thanks