How the S.A.L.T. deduction debate could derail infrastructure reform and last updated 2021-05-14 17:24:00-04 ORLANDO â Let's talk about salt. No, not what you put on food. The S.A.L.T. debate in Washington is about state and local tax deductions and whether Americans should be able to deduct unlimited state and local taxes on their federal tax return. WHY IT MATTERS Former President Donald Trump's signature tax law in 2017 made a change to the amount of state and local taxes that can be deducted from a federal tax return. Prior to 2017, it was an unlimited amount.