The Islamic State is reportedly earning in excess of $1m per day, from the sale of oil, trucked into Turkey, and sold through black-market channels. Though the United States has voiced its strong objections, directly to Turkey's leadership, the illicit commerce, which amount to terrorist financing, continues.
Most observers believes that this illegal oil trade is being allowed to flourish because of these reasons:
(1) Islamic State holds a large number of Turkish diplomats hostage, and the Government of Turkey fears that they will be beheaded, should it incur ISIS anger. This is a reasonable assumption, given the three summary executions of Westerners witnessed lately.
(2) Turkish consumers are actually reaping a benefits from the illicit oil sales, for it has reportedly caused retail prices for gasoline to fall.
(3) A number of wealthy Turkish businessmen, and their PEP associates, have financially benefitted from this technically illegal trade.
Given Turkey's currently frosty relationship with the United States, and the EU, Western influence thus far has failed to cause Turkey to terminate the entry of oil tankers carrying ISIS oil into the country.
Since in Turkey, such activities do not occur without tacit approval of government, and given the history of corruption among the country's PEPs, a significant portion of the oil profits is certainly flowing into the overseas bank accounts of some senior Turkish PEPs. Remember also that the adult children of Turkish ministers have been implicated in massive corruption.
It might be prudent to check all your major Turkish bank clients; has anyone been making large deposits ? Are any wire transfers coming into their accounts from new sources, perhaps ?