What is a critical factor in determining if a taxpayer's Social Security benefits are taxable?

A critical factor in determining if a taxpayer's Social Security benefits are taxable is the taxpayer's combined income. Combined income is computed by adding the taxpayer's adjusted gross income (AGI), non-taxable interest, and half of their Social Security benefits.

When considering taxability, the level of combined income plays a pivotal role; it determines whether the benefits are subject to taxation based on thresholds established by the IRS. If a taxpayer's combined income exceeds certain amounts, a portion of their Social Security benefits may become taxable.

Although age and filing status can influence tax brackets and eligibility for certain tax benefits, those factors do not directly affect whether Social Security benefits themselves are taxable. The main determinant hinges entirely on the combined income figure.

This is why it's essential to understand combined income as a key element in the process of assessing tax liability on Social Security benefits, emphasizing its significance over other factors such as age and filing status.