I just married. My number of allowances is 1, status is single. We want to file jointly. I want to change single to married on W-4 but what about the allowance.

[bryanm3smith]

Do I need to change the allowance to 0 because I'm married now?

[Opus 17]

You should follow the W-4 instructions carefully.  If you have more than one job between the two of you, be sure to fill out the two-earner worksheet, this will give you some adjustments depending on your job income.  The result is a number of allowances to divide between your two jobs; in other words, if it gives you married with 1 allowance, then one spouse would claim 1 and the other spouse would claim zero.

You can also use this IRS withholding calculator that will give you advice on how to change your withholding for the rest of the year.  But if you make changes based on this calculator, you will need to re-run it in January to adjust your withholding for 20108. https://www.irs.gov/individuals/irs-withholding-calculator