In May of 2010, I received a letter from the IRS saying that the amount of my 2009 return that I was expecting was increased because I had missed a credit (that was new that year) and they had computed the new amount for me, which was really a nice unexpected surprise. Last week I received a letter from an IRS office, it was more like a bill, saying that I owe almost $10,000 in taxes on my 2009 return and to send a check by November 26. Obviously if they sent me the original letter saying that I had more money coming to me, someone had to look at my return, figure out that I had not taken that new credit , so how can 4 years later they can say that I owe $10,000 on the same return ??? Shouldnt the original letter I received be proof that I dont owe that money?