It would be easy enough to fake receipts as they go, so relying on surprise would probably be penalizing impulsive fraud over premeditated fraud by people with more resources because they are conducting higher amounts of theft. Kind of a common criticism of the IRS.
I grew up hearing stories of armed IRS agents breaking down doors and carting off all of the paperwork, leaving businesses unable to function. I have always viewed them as jackbooted thugs that could stomp all over your civil rights without consequence, just like the rest of the government.
I'm sure those were all completely above board and reputable businesses getting raided by the IRS, like Mom-and-Pop hardware stores or town doctor's office, and not used car dealers or nightclubs.
What do you know, something good has finally come of modern day scammers.