I think they need to pay a sales tax(idk if it was a state where there's no sales tax or whats sales tax like in US). Capital gains is on the sender, but I have no clue how they're going to track lightning transactions anyway. It's like asking for capital gains on cash transactions which is absurd.

The no tax is due to not all states having a sales tax so that's not an issue. But under IRS guidelines, a person technically must report all crypto transactions including the original purchase price and the price when it was sold / transacted. Not sure how well they track it though.

I don't think Shake Shack would handle it, they probably use a third party to "handle that bitcoin stuff" -

As far as whatever business, yea they gonna have to make sure everything logged right. For the purchaser, for small transactions like this the IRS would never know. We're still somewhat at a voluntary self reporting situation.

give it a month

Getting auditfucked because you bought a burger on May 15 2025 is going to suuuuuck 🤣

You can state your prices as "tax included"; you don't have to state the sales tax separately.