NY Form IT-558 is used to report any New York State addition and subtraction adjustments required to re-compute federal amounts using the rules in place prior to any changes made to the Internal Revenue Code after March 1, 2020.
There are many instances where state tax law treats certain income and deduction items differently from how they are treated on your federal tax return. This is referred to as "decoupling", i.e. when state law differs from federal tax law in a particular situation.
The TurboTax NY state tax interview will determine if decoupling will affect your return - it will ask the necessary questions to determine if any of these differences apply to you.
For additional information, see: What is an IT 558 tax form in New York? and decoupling.
