The reason we've seen such a huge jump in the likelihood of seniors having their Social Security benefits taxed is that the aforementioned AGI thresholds haven't been adjusted for inflation since inception. This threshold was set at $25,000 in adjusted gross income (AGI) for single tax filers and $32,000 for couples filing jointly, and it allowed 50% of Social Security benefits to be subjected to federal income tax. Individual taxpayers earning over $34,000 in AGI, and couples filing jointly making in excess of $44,000 in AGI are subject to this higher rate.