Fortunately, no. The amount of the benefits includible in gross income may be zero, somewhere between zero and 50%, or somewhere between 50% and 85%; 85% is the maximum taxable percentage. The exact amount depends on the amount of your net benefits, your tax-free interest from municipal bonds, and your overall income.
IRA-type plan set up by an employer, rather than the employee. Salary-reduction contributions may be allowed to plans of small employers set up before 1997.