You can wait to change your W-4 anytime you choose to. Your W-4 does not go to the IRS. It only goes to your employer to tell the employer how much tax you want to withhold from your paychecks. You do want to make sure you are having enough withheld to avoid owing tax at tax filing time.
Try the IRS W-4 calculator:
So that you know when it is time to file your 2019 return(s):
Your filing choices will be to file married filing jointly or married filing separately.
Married Filing Jointly is usually better, even if one spouse had little or no income. When you file a joint return, you and your spouse will get the married filing jointly standard deduction of $24,000 (+$1300 for each spouse 65 or older) You are eligible for more credits including education credits, earned income credit, child and dependent care credit, and a larger income limit to receive the child tax credit.
If you choose to file married filing separately, both spouses have to file the same way—either you both itemize or you both use standard deduction. Your tax rate will be higher than on a joint return. Some of the special rules for filing separately include: you cannot get earned income credit, education credits, adoption credits, or deductions for student loan interest. A higher percent of your Social Security benefits may be taxable. Your limit for SALT (state and local taxes and sales tax) will be only $5000 per spouse. In many cases you will not be able to take the child and dependent care credit. The amount you can contribute to a retirement account will be affected. If you live in a community property state, you will be required to provide additional information regarding your spouse’s income. ( Community property states: AZ, CA, ID, LA, NV, NM, TX, WA, WI) If you are using online TurboTax to prepare your returns, you will need to prepare two separate returns and pay twice.
Be careful though if you both have W-2 income. Changing the W-4 to married will result in less withholding and does not account for two incomes that when added together, pushes you into a higher tax bracket and you end up under withheld. Many married taxpayers with tow incomes intentionally use single on W-4 just so that more is withheld.
|Each employer withholds as if that was the only income, but when added together you can move into a higher tax bracket so more withholding (or paying estimated tax) is necessary. When both spouses work they might need to claim single and not exemptions to avoid paying additions tax or even having an addition amount withheld. This is very common with two incomes.|
See this FAQ:
Why did my refund drop when I entered another W-2?