If you hold an interest in a foreign corporation, Form 5471 is probably part of your U.S. filing. Which parts of it you complete depends on the category of filer you fall into — not on the size of the business.
Categories, not size
The categories turn on how you came to hold the interest, how much of it you hold, and whether control changed hands during the year. Two shareholders in the same company can owe quite different schedules as a result.
Why it is worth getting right
Form 5471 carries penalties that apply per form and per year, and they are assessed whether or not any tax is due. An incomplete form can be treated as never filed, which also holds the limitation period open on the entire return rather than on the form alone.
If you have set up or acquired a company outside the United States, send us the structure and we will tell you what the filing looks like.