What percentage of a client's social security benefits may be taxable?

The taxation of Social Security benefits is dependent on the taxpayer's combined income, which includes adjusted gross income, tax-exempt interest, and half of the Social Security benefits received. Generally, up to 85% of a taxpayer’s Social Security benefits can be subject to income tax.

This is applicable for single filers whose combined income exceeds certain thresholds, as well as for married couples filing jointly. The portion that is taxable is calculated based on their total income exceeding these thresholds. Specifically, if a taxpayer’s combined income is above $34,000 (for single filers) or $44,000 (for married couples filing jointly), then up to 85% of their Social Security benefits may be taxable.

Since up to 85% is the maximum percentage of benefits that can be taxed, this makes it the correct choice in this context. The percentages mentioned in the other options do not reflect the IRS guidelines accurately regarding the taxation of Social Security benefits.