@gdpaull , having gone through your post and the response from @MinhT1 , while I agree with her answer , I would like to add a little. If your spouse is a wage earner, she MUST file a W-4 -- required for each wage earner. What you can do is to adjust the total taxes withheld-- i.e. the two W-4s should be sufficient to cover the total wages for the year ( each pay period ). IRS has a calculator for this -- see https://www.irs.gov/individuals/tax-withholding-estimator
What law requires is that the expected tax liability be withheld-- however people often allow the employer to withhold more , so as to get a refund at the time of filing.
Note that if your spouse does not file a W-4 with her employer, then the employer is obligated to withhold as if she was single ( generally leading to higher refund at filing but less cash during the year )
