I hope this will help by showing you how the taxable amount of social security is determined.
Taxable social security income applies if when half of the social security income is added to the other income exceeds the base amount of $25,000 ($32,000 for married filing jointly). This would mean that up to half of your social security income could be included as taxable income. And then, if that total exceeds the next level base amount of $34,000 ($44,000 for married filing jointly) it can be taxed at a maximum of 85% of the total social security benefits.
This will fluctuate based on the other income on the return. Tax exempt interest is included in the "other income" category and certain adoption benefits as well as foreign income exclusions are added back.
For more information you can click this hyperlink: Publication 915
