NEW YORK — An ING Groep unit that administers 401(k) retirement plans has agreed to pay $5.8 million to settle allegations it didn’t tell clients that it would pocket market gains on trades that were delayed.

ING Life Insurance & Annuity Co., a Windsor, Conn.- based unit of the largest Dutch financial services company, will pay $5.25 million to about 1,400 retirement savings plans and a penalty of $524,509 to the US government, according to a settlement disclosed Monday by the Department of Labor.