Abu Saleh was killed in late November, US military spokesman Colonel Steve Warren said in a videoconference from Baghdad, calling him "one of the most senior and experienced members" of the group's financial system.
"Abu Saleh was the third member of the finance network that we have killed" recently, Warren added, likening him to a finance minister for the extremist group, which has grabbed swathes of Iraq and Syria in a brutal offensive of beheadings and forced religious conversions.
Abu Saleh was killed along with two associates as part of the US-led coalition's campaign to destroy the extremists' financial infrastructure, said Brett McGurk, Washington's envoy for the anti-ISIL fight, on Twitter.
Real name Muwaffaq Mustafa Muhammad al-Karmush, Abu Saleh is described on the US State Department's terrorist blacklist as a 42-year-old Iraqi.
"Killing him and his predecessors exhausts the knowledge and talent needed to coordinate funding within the organization," Warren said, adding that two other men pivotal in ISIL fundraising networks also were killed in coalition airstrikes in Iraq in late November, AFP reported.
They were identified as Abu Mariam, an enforcer and senior leader in the ISIL group's extortion networks, and Abu Waqman al-Tunis, who Warren said coordinated the group's transfer of people, weapons and information.
Abu Mariam appears on the State Department terrorist list as Mounir Ben Dhaou Ben Brahim Ben Helal, a 32-year-old Tunisian.