An inheritance can include a company, if privately held. That company has a value, and that's taxed through inheritance tax.

The problem is that a company of value $x rarely has liquid assets of $x*$taxrate, so inheriting a company can mean personal ruin.

On the _other_ hand, not accounting for companies in inheritance tax means that every family ever will shift all its possessions into a company.

Roughly speaking, Germany solved this by creating a set of exceptions for value "in a company", as long as it continues to be held for a given number of years (otherwise, since it was sold, it's considered a liquid asset and thus fully taxable).