Like any good legal answer, it depends.
Back pay = Congress has provided a special provision for lump sum payments that cover several prior years. SEE I.R. Code ch.86(e) It allows the taxpayer to offset the lump sum
SSA will send you a 1099 each year. These forms are often inaccurate and you need to check them carefully.
The basic rule =
Up to 50% of SS benefits are taxable if your total income exceeds a base amount. ($25,000 for single people and $32,000 for married filing jointly)
Up to 85% of SS benefits are taxable if your total icome exceeds a base amount. (over $34,000)
THE OFFICIAL LAW FIRM OF THE TEXAS RANGERS