1. Increase in Standard Deduction
Taxpayers have two options when they file their federal income tax returns: take a standard deduction or itemize deductions.
With TJCA, the standard deduction available for taxpayers became nearly twice its previous amount. For 2019, the standard deduction is increasing to $12,200 for individuals, from $6,350 (pre-TCJA) and $24,400 for married couples filing jointly. When you itemize, you basically add up a number of different deductions instead of taking one fixed dollar amount as with the standard deduction. One typically selects the option that reduces their overall tax liability the most.
This increase in the standard deduction makes it less likely that the sum of a taxpayer's itemized deductions will exceed the larger standard deduction, especially with new limits in place on deductible state, local or property taxes (cap of $10,000).
A potential side effect of fewer taxpayers itemizing their deductions is that these taxpayers may choose to reduce contributions to charitable organizations because their contributions will no longer reduce their personal income taxes.