I recently looked in to this and found…
(1) Exemptions aren’t a thing anymore – but they still exist (keep reading).
(2) The new 2020 W-4 doesn’t include any reference to exemptions.
(3) The new 2020 W-4 includes a new choice for withholding. Married and Single as before but now there’s a choice for Head of Household.
(4) All new W-4 forms that you submit to your employer must be the new 2020 exemption-less W-4 forms.
(5) Your employer can request a new W-4 from you because of the change, but you aren’t required to provide one if the employer already has a pre-2020 W-4 on file.
(6) If you’re a new hire or you want to adjust your withholding you MUST use the new 2020 W-4.
(7) Your employer will withhold from your paycheck using the new 2020 W-4 if they’ve got it, or they’ll use your old exemptions if you had previously provided them a pre-2020 W-4. In this regard, exemptions still exist.
I used Publication 15-T to figure out how the new W-4 worked as it pertains to employer withholding. (A link to the PDF is below.) Starting on page 5 you’ll see how your employer will use the information you provide on the new 2020 W-4 (or the old pre-2020 W-4) to calculate your withholding. I’ve already estimated my 2020 tax liability and I know how much I need to have withheld from my check to accomplish my goals. Knowing this, I used page 5 of Publication 15-T to reverse-engineer the 2020 W-4 form so I knew what numbers to supply on my new 2020 W-4 to have my taxes withheld exactly consistent with my requirements.
IRS Publication 15-T
My impression of the new 2020 W-4 is that it does an excellent job of withholding the exact right amount of taxes if you fill it out correctly. It also improves the accuracy of your employer’s withholding under a couple of circumstances that the previous W-4 didn’t. Specifically, anyone who’s Head of Household benefits by the change because you don’t have to tamper with exemptions to correct for a lack of Head of Household choice as was necessary with the previous W-4. Secondly, it seems like the new W-4 handles married employees that have both people working so the tax withholding would be correct for the household.