When you win at online casinos you will be requesting a withdraw payment. This normally only takes a few days to process depending on the casinos you play at. RTG online casinos can be very slow at payments on your withdraw and they may not pay all in full. Playtech has the same issues, some of the online casinos will only pay a up to a certain amount every month and who knows if they will still be in business months from now. Microgaming online casinos are no doubt the best at withdraw payments. Yes you will have to fax back some documents but you will receive your payment within a few days in FULL.
Seriously, after years of playing online I have learned the hard way about bad online casinos. So please take my advice, if you want to gamble online do it at microgaming casinos as they will pay your wins, and the casino games are fair plus they have the best selection. I would not play anywhere else.