Just look at the photograph in which the sun beam illuminates all of those little yellow envelopes (they look just like the envelopes at Forest Service campgrounds) provided to Mike Castro by his customers with the $4.00 inside. This is evidence of the records that Mike Castro receives from his customers of the cash receipts. This evidence is then destroyed by Mike Castro as he evades any income tax on these cash profits.
There is the evidence of the destruction of records to effect the tax evasion scheme.