How Social Security Benefits Create Hidden Tax Traps for Retirees

Full analysis

Rick Connor, writing at HumbleDollar and drawing on experience preparing hundreds of AARP TaxAide returns, illustrates how Social Security benefits interact with other income to create surprising tax bills — or surprising savings. Up to 85% of Social Security benefits can become taxable depending on total income, and the type of additional income matters enormously: a couple with $50,000 in Social Security and $100,000 from a traditional IRA distribution owes roughly $10,907 in federal tax, while the same couple taking the same $100,000 as a Roth IRA distribution owes $0, and taking it as long-term capital gains (profits on investments held more than a year, taxed at lower rates) also owes $0 — a difference of nearly $11,000 from the same dollar amount of income.

A 2025 tax law adds a $12,000 senior deduction for couples 65 and older filing jointly, which raises the threshold at which any tax kicks in. Connor also shows a real-world application: when his mother-in-law's dementia care costs qualified as medical deductions, that allowed the family to pull money from her traditional IRA and harvest investment gains — both tax-free — by stacking the medical deductions against income that would otherwise have been taxable. The core lesson is that in retirement, the sequence and source of withdrawals — traditional IRA, Roth, or taxable investment account — can shift the tax bill by thousands of dollars, and the interaction with Social Security taxability makes this more complex than most people expect.