A retiree who has already paid 2 quarters worth of estimated taxes - both federal & state - is going back to work. How does the soon to be exretire figure how many W2 deductions to take?

When I was in this situation I claimed zero allowances on my W-4. When calculating my ES payments I had already taken into account my exemptions and deductions, so there was nothing to consider on the W-4. (Without calculation I could have claimed one allowance on the W-4, in accordance with the instructions.) I was able to stop making estimated tax payments because the withholding would more than keep me safe for the previous year's tax safe harbor.

The most important calculation was one not required by any immediate action. I estimated the entire year's earnings and withholding/estimated tax payments. That told me how much money I needed to set aside to have the money available to pay my balance due come April.

Phil