New Job, new percentage question for W4

[AZJeep]

Hello,
My wife started a new job, trying to fill out the W4.
We fall in the 12% tax bracket, with both incomes.

Here's the rub and the crux of my question; I'm disabled and on SSD, I do not get Federal withheld and do not want to change that. My wife does not want to list that on her W-4, new employer and all.

I am lost as to what to do with her W4, I went to the Federal website to find out we are in the 12% bracket but have no idea what to put on the W4 without putting the amount I get from SSD as non-taxable.

I *think* we need to put extra tax to be withheld from each pay period, but how do I figure that amount?

My wife explained the situation to her old employers payroll clerk, the clerk had it set up so that we received a small refund from Federal every year but my wife isn't sure what she did. The new employer is a larger company and is not willing to give any advice, the way I understand it, they do not want hassle if it's not the correct answer. Allegedly the payroll manager at the new job can't just put in a percentage, but I don't know that for sure.

So, how do I figure out the amount that needs to be deducted pay period ( 15th and 30th (semi-monthy?)). SSD just had a cost of living increase so that adds to my confusion.
I can't find how much will be withdrawn from first check (standard amount deducted).
Trying to find percentage deducted from old job but not sure if I'm doing the math right.
When figuring out the percentage taken from her old job (adjusted gross), do I add Fed, SS, Medicare, and state (based on what I could find on google search)? If I do that they were taking 22% that seems too high because together in 2021 we were under $75,000, with a few hundred dollar refund.
Percentage of Federal only was 11% in 2021.

AZ has a separate A-4 that has choices of withheld amounts, seems to me they'd be separate, but I admit, what do I know...
Note: Using 2021, 2022 her old employer was sold, she didn't work full year, other factors so I just used 2021.

I'm just lost, I'm not sure how to go about this without owing a substantial tax bill next year.

Any help would be greatly appreciated

if it matters, using TurboTax Deluxe, have used it since the late 1990's

[JohnB5677 · Accepted solution]

If your combined income, not including SSDI. exceeds $32,000, the SSDI starts to be taxed.  Only 50% starts out being taxed, but it can get up to 85%.  The calculation is complicated, but I wanted you to be aware that it can be taxed.

The Form W-4 gives you two areas that will accommodate your SSDI anonymously.

In step 4 you can have taxes taken out for "Other Income". 

• There is no indication on the form indicating where it came from. 
• If you want to be safe, I suggest you enter a value that is 85% of your SSDI, plus any other interest, dividends or miscellaneous income you may have.

The second alternative in Step 4 is to have an additional amount taken out in each pay period.