Social security can become taxable if a person has a certain level of income in retirement. Retirement income from pensions or 401(k)s and other taxable sources will contribute to the AGI of a person in retirement, but it will not ever disqualify a person from receiving their social security check in retirement if it is owed to them.

Instead, social security benefits become taxable as income if a person has enough income in retirement to trigger the social security taxes. The level is actually quite low, and has not been adjusted for inflation recently.

Half of a person’s household social security income will be added to the taxable income from other sources, and for those whose income using that formula is over $44,000, up to 85% of their social security income becomes taxable. Roth IRAs and life insurance cash value loans are the only sources of income that are not included in this calculation of income.

Notably, tax-free muni bond income is included. Considering the amount that many people have paid-in to social security over the years, this tax treatment can be an unpleasant surprise for many Americans.

How Does My Retirement Age Impact My Social Security Benefits?
When Will Social Security Go Bankrupt?
Are Social Security Benefits Taxed?