According to the Rabbis, the laws of tithing only apply to the land of Israel, and farmers in the Diaspora have no obligation to give tithes, although there is some evidence of communities outside Israel, in Egypt for example, having a system of tithing.
Again according to the Rabbis, the full tithing laws apply only when the majority of Jews live in the land of Israel and since, in the absence of the purification rites of the red heifer, everyone today suffers from corpse contamination, the terumah is inoperative in any event. Moreover the purpose of tithing, for the upkeep of the priests and Levites, has no meaning nowadays. The present practice in the State of Israel is to have only a token separation of the tithes.
Some Rabbinic sources make reference to a tithe of money as well as of produce, although it is not too clear whether this was seen as a voluntary contribution rather than an obligation. Nevertheless, many observant Jews today do donate a tenth of their annual income to charity. This is known asmaaser kesafim, 'the money tithe' or 'wealth tax.'