"[Y]ou have to determine annually whether you are a 'large' plan or 'small' plan for filing purposes. The good news is that you can determine 'large' plan status on the first day of your plan year, and you don't have to wait until after the plan year-end when your 5500 is being prepared.... [A] plan may continue to file as a small plan filer (and thereby avoid the requirement for an audit) as long as there are between 80 and 120 participants at the beginning of the plan year. This is especially important for plans in which the participant count may tend to hover around the 100 participant threshold."