TD Ameritrade Holding Corp. has entered into an agreement to acquire a portion of Fiserv, Inc.’s Investment Support Services business.

The firm will pay $225 million in cash for the businesses and up to an additional $100 million based on achieving revenue retention targets. In addition, the company will reimburse Fiserv for capital remaining in the business at close. The transaction is expected to be immediately accretive.

The acquired businesses include approximately $28 billion in client assets, including $17 billion managed by 500 independent registered investment advisors and $10 billion held in 2,200 plans administered by 80 independent third party administrators.

TD Ameritrade says that the transaction will solidify its position as one of the leading providers of trading and custodial services to RIAs. TD Ameritrade will also become one of the five largest custody and clearing trust providers for retirement planning services, significantly advancing the company’s scale in this business.

“RIAs make up one of the fastest-growing client segments in financial services, and we are committed to intensifying our position in the space and further advancing our client segmentation strategy,” said CEO Joe Moglia.

“We’re confident that the Fiserv client base will benefit from our industry-leading technology, flexible service and ongoing advisor advocacy efforts,” said Tom Bradley, president, TD Ameritrade Institutional.

The transaction is expected to close in four to six months, following regulatory approvals.