Though most people consider gambling a form of entertainment, real money is won and lost at casinos. In most countries like USA both the federal and state government impose taxes on the casino winnings and the casino is supposed to withhold the tax amount from the amount paid to the winner.
This law is applicable to foreigner who may win a small amount at one casino, only to lose a larger amount at some other casino. However the US government has tax treaties under which citizens of Canada, Japan, Russia and other European countries can get casino tax refunds by completing the necessary paperwork.
Services like CasinoTaxRebates assist eligible foreign winners at casinos in getting their casino tax rebate. They greatly simplify the process by coordinating with the relevant government authorities.