I found this on the SSA site: http://www.ssa.gov/pubs/10035.html
If you scroll to the bottom you will see what I pasted here.
Your benefits may be taxable
About one-third of people who get Social Security have to pay income taxes on their benefits.
- <LI class=ninetypercent>If you file a federal tax return as an “individual,” and your combined income* is between $25,000 and $34,000, you may have to pay taxes on 50 percent of your Social Security benefits. If your combined income* is more than $34,000, up to 85 percent of your Social Security benefits is subject to income tax. <LI class=ninetypercent>If you file a joint return, you may have to pay taxes on 50 percent of your benefits if you and your spouse have a combined income* that is between $32,000 and $44,000. If your combined income* is more than $44,000, up to 85 percent of your Social Security benefits is subject to income tax.
- If you are married and file a separate return, you probably will pay taxes on your benefits.
At the end of each year, we will mail you a Social Security Benefit Statement
(Form SSA-1099) showing the amount of benefits you received. You can use this statement when you complete your federal income tax return to find out if you have to pay taxes on
Although you are not required to have federal taxes withheld, you may find it easier than paying quarterly estimated tax payments.
For more information, call the Internal Revenue Service’s toll-free telephone number, 1-800-829-3676
, to ask for Publication 554, Tax Information For Older Americans
, and Publication 915, Social Security Benefits And Equivalent Railroad Retirement Benefits
*On the 1040 tax return, your “combined income” is the sum of your adjusted gross income plus nontaxable interest plus one-half of your Social Security benefits.