I'm not understanding something you say the S-Corp election was made in 2007 and were owned by your parents. then at some point afterwards(?) they died and you inherited some or all of the shares.
the confusing part is you also say you owned share since the election was made which seems to contradict the prior sentence.
shares you inherited start off with a tax basis of their Fair Market Value on the date you inherited them which would be the date of death of each parent for the shares that you inherited from each. You'll need professional help in determining those values. From there tax basis goes up and down depending on what each k-1 you get shows.
If you don't do this, you likely misreport what your actual gain loss is upon liquidation of the corporation.
Put another way your outside tax basis is likely not the same as the book value of those shares.
