My stae also has a line on my taxes for me to declare and pay sales tax on anything I bought out of state that year. How many people do you think accurately fill that line out?

Tips are effectively tax free as reporting rates are abysmal.

How would this realistically be enforced though without there being a paper trail at all?

Kudos to those honorable people that do declare tips on their tax return though.

There's a default rate (percentage) that gets used in the event of an audit, I believe.

If you are somewhere that tracks your individual sales, you'll get hit with this.

To be fair, the rate is pretty low and so almost everyone will still have a large percentage of their tips go untaxed.

How much tipping these days is cash vs card? I would imagine that cash tips are underreported on tax forms.

Credit tips are cashed out at the end of the day, generally speaking, so that the "credit tips" are offset by unreported "food cash payment" that sits in your pocket all night. (I believe it also relies on the business underreporting sales, but... Cash. Also likely hiring the wait staff under the table)