To complete a retroactive R&D study, required accounting documents will vary. In a perfect world we would have all tax returns, W2s, and time tracking information back to 1984 or when the company started (whichever came second). Obviously, this is a bit of a pipe dream, and the IRS agrees. There are several ways to work around missing accounting records, though we will go to great lengths to recover historical records. However, sometimes we have to forgo retroactive credits and concentrate on claiming the credit going forward.