Complectus, which owns trustee firm Perpetual Guardian, has signed a heads of agreement with Covenant Trustee Services as it continues its purchasing spree of supervisor services firms that began with the acquisition of Perpetual Trust in 2013.

A sale process is expected to conclude later this year, which will expand Complectus's offering in the fiduciary services sector, and give the firm about 55 percent of the country's retirement village supervision, the company said in a statement. If it goes ahead, Covenant would remain a stand-alone business within the Complectus group.

"The expected purchase of Covenant presents the opportunity for Complectus to expand our footprint in the fiduciary services sector, and also offer a wide range of benefits and advantages to Covenant clients," Complectus managing director Andrew Barnes said. "We will be in a position to update the market later in 2015."

Last year Complectus bought out Milford Asset Management's active growth wholesale fund's stake in Guardian Trust, which the pair had bought for $68.5 million. The deal allowed Complectus to combine Guardian with Perpetual Trust, which Barnes bought the year before from Pyne Gould Corp.

The operations of Perpetual and Guardian are still being combined, which Complectus said will create the country's leading statutory trust business.

Covenant is wholly-owned by Fancourt Investments, a vehicle for the trust firm's managing director Graham Miller, Raewyn Miller and Alan Calvert.

Miller said the heads of agreement will give the firm access to additional resources, and allow Covenant to maintain the same service and brand due to the lack of overlap between the businesses.

Miller will continue to be involved in the business, the statement said.