How to correctly fill out W-2 if no federal tax is taken from my pay. My wife and I both receive social security and pay tax on it.

[xmasbaby0]

You do not fill out a W-2.   A W-2 is a tax document issued to you by an employer to show how much you earned and how much tax the employer withheld.   YOU may fill out a W-4 for an employer to tell the employer how much tax to withhold from your paychecks.

You say that you and your spouse are both receiving Social Security----if SS is your ONLY income it is not taxable.  If you have other income along with the SS, then the SS may be taxable.   So......you can have tax withheld from your SS---which you must arrange through Social Security---or have more withheld from your W-2 job to help you avoid a big tax bill or underpayment penalty at tax time.

https://turbotax.intuit.com/tax-tools/calculators/w4/ 

https://www.irs.gov/individuals/tax-withholding-estimator

https://www.irs.gov/pub/irs-pdf/fw4.pdf

You could use Step 4 (c) to have extra tax withheld from each paycheck.

[NateTheGrEAt]

When completing a new W4 in this situation, Step 1, 2, and 3 are completed using your personal information as may be accurate.  You didn't mention whether you are wanting to have taxes withheld from your paychecks to not only cover the tax on your pay but also on your Social Security. If you do want that, then complete Step 4(a) with the amount of taxable Social Security from your previous tax return. You could find that amount on line 6b of your 2023 Form 1040. Note that if you file jointly, the amount on the 1040 will be the combined amount of taxable Social Security for both you and your spouse. If you both want to have taxes withheld from your pay to cover the tax due on Social Security, apportion the amount between you and each fill out your own amount of taxable Social Security in Step 4(a) when completing your own W4.