Originally Posted by Tyro
I kept meticulous records too, but when I went to redeem shares last year & early this year, 3 different companies told me I had to use average cost for shares purchased before 1/12. If they all told me wrong, I don't know what, if anything, I can do about it now.
They told you wrong.
What to do about it: Ignore them and report the basis you can document. As long as you have never used average basis for that mutual fund in that account on your Schedule D to tell the IRS that you are using average basis, you are good to go. This has been detailed for years and years in the Schedule D instructions and probably continues in the newish 8949 instructions as well.
Also read publication 550. A nice discussion starts on page 46.