Forms 1040 and SSA-1099 are required to complete the Internal Revenue Service Social Security Benefits Worksheet. If the taxpayer also receives railroad retirement benefits that are treated as social security, Form RRB-1099 is needed as well.
The IRS Social Security Benefits Worksheet is used to determine if social security benefits received by an individual are taxable and what percentage of the benefits are subject to taxation. Social security benefits are only taxable when the annual income of an individual passes certain thresholds that differ depending on his filing status. The total amount of benefits an individual receives is reported on Form SSA-1099 and is added to any additional income reported on Form 1040 in order to determine the total annual income.
In 2015, taxpayers whose annual income is between $25,000 and $34,000 and who file as an individual pay tax on up to 50 percent of their social security benefits. When the annual income passes $34,000 for an individual, up to 85 percent of the benefits are taxable. Those who file a joint return with a combined annual income between $32,000 and $44,000 pay tax on up to 50 percent of their benefits. When the combined income is more than $44,000, joint filers pay tax on up to 85 percent of their benefits.