150 Milk St. in Boston's Financial District. Photo courtesy of Google Maps

Two office buildings in downtown Boston would be converted into 101 apartments under the most recent proposals responding to Boston’s offer of property tax breaks to spur adaptive reuse of underutilized downtown buildings.

KS Partners submitted its third application under Boston’s residential-to-office conversion program for 15 Court Square in Downtown Crossing, where it plans 80 apartments on the upper floors of the 87,546-square-foot building.

The company plans to negotiate lease terminations with 14 commercial tenants, according to a filing with the Boston Planning & Development Agency. Average rents for the market-rate units would range from $1,499 to $4,800, KS Partners estimates.

The estimated project cost is $27.9 million.

KS Partners previously received approval for 95 apartments in an office conversion at 85 Devonshire St. and 258 and 262 Washington St.

At 150 Milk St. in the Financial District, Newton-based Wingate Cos. said it will terminate leases for three tenants occupying 10,700 square feet, or half of the 6-story building, to create 21 studio and one-bedroom apartments.

The company estimates average rents of $2,058 and $3,150 per month for market-rate units. The $9.2 million project also includes three income-restricted units and one apartment for a housing voucher holder. Wingate will seek historic tax credits as part of its financing strategy, according to an application submitted to the BPDA.

Gov. Maura Healey has scheduled a press conference with Boston officials today to discuss a state partnership with the city on the downtown residential-to-office conversion program, which is nearing the end of a pilot period.

The Boston program offers 75 percent abatements on property taxes for 29 years.