The Halacha prohibits conducting business transactions, "Mekach U’Memkar," on Shabbat. In the era of e-commerce, many new questions arise. For example, the Poskim discuss whether it is permissible to leave a PayPal account active on Shabbat. The issue is whether any money deposited on Shabbat or Yom Tob constitutes a prohibited transaction.
The consensus is to be lenient, provided the Jew did not instruct that the money be deposited specifically on Shabbat. The precedent for this ruling is found in Shulhan Aruch (Siman 246), where Maran permits giving money to a non-Jew to make a purchase, without specifically indicating to do so on Shabbat. The fact that the non-Jew actually bought the items for the Jew on Shabbat is inconsequential. Maran also rules (Siman 243) that the only reason it is prohibited to hire a non-Jew to manage a bathhouse is "Marit Ayin," people may misconstrue the arrangement. He does not cite the problem of the non-Jew receiving the money on the Jew’s behalf. From these precedents, it is derived that one may leave his PayPal account active on Shabbat, and any money deposited on Shabbat is permitted for use immediately after Shabbat.
SUMMARY
It is permitted to leave a Pay Pal account active on Shabbat.
