I have a question on the cost basis reported on my 1099-B forms. I sold some of my shares of a mutual fund on 8/1/12 and calculated my average cost tax basis using the average cost of all shares purchased prior to 8/1/12 in that calculation. My 1099-B seems to be calculating average cost with only those shares purchased prior to 1/1/12, or the "non-covered" period. It is therefore excluding some purchases made between 1/1/12 and 8/1/12 that would increase my tax basis. I know this doesn't get reported to the IRS this year, but it will likely result in a difference between my tax basis and theirs going forward into the "covered" period as well. Has anyone else encountered this, and know is either or both approach correct? In prior years I never had any differences between my cost basis and what my funds have reported to me. I have e-mailed the brokerage as well to see why they are making a distinction between the covered and non-covered periods.