Four Deaconess Hospital employees say their jobs are being threatened because they didn’t pay union dues during a nine-month period when there wasn’t a labor contract between the hospital and Service Employees International Union 1199NW.

The employees, who are not union members, filed a complaint with the National Labor Relations Board, alleging unfair labor practices.

In Washington and other states that don’t have right-to-work laws, nonunion employees can be forced to pay dues to keep their jobs, according to the National Right to Work Foundation in Virginia, which is providing free legal assistance to the Deaconess employees. But nonunion employees do have the right to opt out of dues for activities that aren’t related to workforce bargaining, such as political lobbying.

In addition, nonunion employees can’t be forced to pay dues if the union doesn’t have an active bargaining agreement in place, the foundation’s attorneys said.

According to the complaint, the hospital and the union took a “contract hiatus” for nine months from July 2013 to April 2014. When a new contract was signed in April 2014, it purported to apply retroactively, the complaint said.

The union sent the employees letters, asking them to pay the back dues, according to the complaint. The hospital sent the employees emails this month, saying they would lose their jobs on May 28 if they didn’t pay the dues, the complaint said.

Deaconess and union officials said they are reviewing the complaint, which they received Tuesday.

Rachelle Delcambre, a delegate for SEIU 1199NW, said the union takes the allegations of unfair labor practices very seriously, but also thinks that all employees who benefit from contract negotiations should pay dues. SEIU 1199NW represents a broad array of health care workers.

The employees who filed the complaint are Nina Bennett, of Colbert; Tori Denniston, of Spokane; Ryan Reedy, of Elk; and Edgar Schlittenhart, of Newport, Washington.