Reliance Health which has five properties in Norwich totaling more than a million dollars is especially concerned.
The COO tells News 8 the paperwork for renewal for tax exempt status with the city was submitted in time and they are now looking into how this could have happened.
Some of their properties were denied by the city assessor while some were not.
The state requires non-profits to reapply for tax exempt status with their local municipality every four years and 2017 was the latest year to do so.
According to The Day, nearly three dozen nonprofit arts, human services, health, veterans, religious and educational organizations will be taxed this year under sweeping decisions by Assessor Donna Ralston to deny tax-exempt status or rule them ineligible for failing to file required paperwork.
The list includes long time institutions, such as Norwich Arts Center, Bethsaida Community Inc., Reliance Health, four lots owned by Norwich Free Academy, two Veterans of Foreign War posts and an American Legion hall.