The exact wording of the law actually stipulates a $6,000 tax deduction for individuals aged 65 and older, likely raising the number of seniors who won't pay taxes on Social Security to 88 percent. Currently, 64 percent of seniors already don't pay taxes on Social Security benefits.

The Trump bill — which was enacted in early July — introduces an additional tax deduction for taxpayers who are 65 or older. The deduction could be up to $6,000 for an individual tax filer and up to $12,000 for a married couple if both spouses qualify.