"it is the 12-month period beginning on July 1"

That's interesting. I always start counting from the filing date, not the tax year, anyway. Then, you have to consider audits: 3 years lookback + 3 more if they don't like what they find at first. And for me, the worst is when I confirm with a client they don't need anything returned, so I shred their stuff, and later they call and ask for it.