In 2022, I filed a IL-1040-V, where do I input that payment?

You do not enter that anywhere.  The federal tax due that you paid for 2022 is not deductible.

@dtabak 

Oh...are you in one of these states?

There are several  states that allow you to enter the federal tax you paid on your state return--Alabama, Iowa. Missouri, Montana, and Oregon.  If you are filing in one of these states watch for the deduction when you prepare your state return.

@xmasbaby0 that's the Illinois form to pay the Illinois balance due by mail.  so if the taxpayer itemizes that could increase his schedule A tax deduction for 2022. I'm assuming that it's a 2022 payment for the 2021 balance due

@dtabak see above. the payment is entered on the tax payments worksheet in the section for prior year taxes paid in 2022. it will only help if you itemize your deductions and your tax deduction of schedule A for 2022 is not already $10,000