"Not determined" is an indication that not all of the facts are available to figure the taxable amount. If you are a retiree, your Benefits Letter may help you calculate the amount. You may also wish to consult the following IRS publications: #571—Tax-Sheltered Annuity Plans (403(b) Plans) for Employees of Public Schools and Certain Tax-Exempt Organizations; #575—Pension and Annuity Income; #590-A—Contributions to Individual Retirement Arrangements (IRAs); #590-B—Distributions from Individual Retirement Arrangements (IRAs); #721—Tax Guide to U.S. Civil Service Retirement Benefits; and #939—General Rule for Pensions and Annuities.