are negative taxes a real thing currently?
Not sure if it would technically be considered a negative tax, but the effect is similar.
In Pakistan, electricity rates are slabbed. 0-100 units are charged very little - often below cost of providing the electricity. 100-200 units more, etc. So ultimately, high consumption users subsidize low consumption users. It makes sense because low consumption users are 'using' cheap electricity from hydropower/gas, but high consumption users are forcing the state to turn on expensive oil based power plants.
But, again in Pakistan's Punjab province, at restaurants, if you pay by cash, sales tax is 19% and if you pay by card, sales tax is 5%.
It's a method by the state to increase the size of the formal economy.