Just leave it to them AND save some money. Once they want the money they want it pretty quickly.
I just paid 8000 chf more than I calculated for 2005 / 2006 and I had 30 days to pay it. This came at the same time as the Bundessteuer 2007, final Gemeinde / Kanton tax 2006 and some money I was still paying for 2007. Plus I am saving for 2008 as it all has to be paid by October 31st. It never seems to stop once it has started !!