What does Go Live really mean?

If you are in the process of selecting a new financial system, or have already selected a solution, how are you approaching your implementation plan and timeline? For many companies on a calendar fiscal year, this is now Q4. If your CFO says s/he wants to be live 1/1/2016, how do you approach this with your implementation partner? For example: 1. What really does "go live 1/1/16" mean? 2. Seeing as the Dec 2015 books won't have been closed, what do you need from the new system on the first working day/week of Jan 2016? -Could it be that you need only to bill customers, apply cash, enter vendor bills and pay them at this stage? -Can you wait until later in January to load opening balances (from 12/31/15)? 3. How do you plan to adjust for 2015 audit adjustments? 4. Isn't your January close and reporting the final stage of "go live" where you prove you have stopped using the old system? 5. How does the size and complexity of your organization influence your decision? 6. Go back to Q1 and see if you would answer it differently after Q2-5. Look forward to the debate!