New York--Efinanceworks L.L.C. announced it will close and return $150 million in venture financing to its backers, Capital Z Partners, General Atlantic Partners L.L.C. and iFormation Group. Efinanceworks was formed last year to invest in online financial services start-ups. Efinanceworks will pass on many of its projects, investments and partner companies to its backers. While the b-to-b e-finance space is expanding, big firms such as LabMorgan, the e-finance and incubator arm of J.P. Morgan Chase & Co. are increasingly dominating it.