Will these receipts still be good for tax purposes.

The Internal Revenue Service wants us to keep our receipts for several years, but I can't recall exactly how many, so if anybody knows how long I should retain these, please let me know. I have been keeping them for my father and his father before him, as I have some of farm property they used to own, so want to use all possible deductions. I am no sure how to get a hold of Dr. Dutson; Jack Cotton or Elden Johnson, but hopefully I can use them as references if need be.