I don't know about the loss part, but while you will fill in your 2012 return in 2013, you will need to pay preliminary tax for 2012 when you do you pay & file now for 2011.
Preliminary tax is prepaying an estimate of your 2012 tax - usually worked out as either 90% of what your total tax for 2012 will be, or 100% of what your 2011 tax is.
So your first tax return is the only one that tends to involve paying 2 years tax at once, as in subsequent years, you are mainly just paying a preliminary tax estimate for the current year and any difference between the previous year's preliminary estimate and the actual amount (which could be a refund if you overestimated)