258 and 262 Washington St. (right) seen in 2022. Photo by James Sanna | Banker & Tradesman Staff / File

A three-building downtown Boston office portfolio will be auctioned off next month despite its approval under the city’s incentive program for residential conversions.

Apex Commercial Exchange will open the online auction on June 15 for 85 Devonshire St., 258 and 262 Washington St. with an opening bid of $3 million.

“We think it’s a smart play for an office investor, or a residential investment group,” said Kevin Lipson, CEO of Brooklyn, New York-based Apex Commercial Exchange.

CBRE’s Boston office is the local marketing agent.

The current owner, KS Partners, received approval for an estimated $36 million residential conversion in 2024. The portfolio contains three connected 11-story buildings completed in 1899.

The approved residential conversion plan includes 54 one-bedroom units, 29 studios and 12 two-bedroom units. It sits across the street from the city’s largest conversion proposed in Boston to date, Synergy’s 255-unit 294 Washington St. project.

Under the incentive program, qualified projects receive 75 percent property tax abatements for 29 years.

After initially being limited to the downtown area when it launched in late 2023, the office to residential conversion program has been expanded to a citywide scope. The Planning Department accepted its first application for a residential conversion in East Boston this month.

The Wu administration extended the incentive program application deadline last December through the end of 2026, after receiving applications for 1,517 new housing units in 27 buildings in the first two years. City data says 31 buildings have now been proposed for conversion so far, for a total of 1,785 units. Six projects are under construction and one has been completed.