One of Boston’s biggest office landlords has made a foray into the local multifamily market with the $123.25-million acquisition of a Jamaica Plain apartment tower.

The pending sale of the 195-unit Serenity complex at 105 South Huntington Ave. riled affordable housing advocates because the previous owner and original developer, Brookline-based Longwood Group, had failed to submit its $8.4 million affordable housing payment to the Boston Planning and Development Agency more than a year after completion. The “cash-out fee” is imposed on multifamily projects that don’t include income-restricted units and supports affordable housing in the same neighborhood.

BPDA spokeswoman Bonnie McGilpin confirmed that the payment was submitted on Jan. 8, a day before the closing. The payment will support development of an estimated 42 affordable units.

The 246,186-square-foot complex boosted occupancy in June 2017 by leasing 24 units to Churchill Corporate Housing.

Oxford Properties Group, a real estate arm of the Ontario municipal pension fund, owns 4.5 million square feet of commercial real estate in Greater Boston.