i work in a off licence we show due diligence by recording all the refusal to serves this shows the authorites that you do check the age of people by not serving underage
Depending on the size of company to be taken over, this can vary from a short enquiry to an investigation of gargantuan proportions, where every department will have to answer a long list of questions about marketing & sales, logistics, employee relations/salary/pension policies, manufactuing processes, etc.
Believe me, it's not something you would put your hand up and volunteer for if you're on the receiving end of the process!