To claim a dependent on a tax return they must have either a Social Security number or an ITIN issued by the IRS.
If your son was born in 2023 the normal procedure is that the hospital will submit the information to the Social Security Administration to get him a SS number. The SS card should be mailed to your home address.
You may want to file for an extension if you do not think the SS card will be arriving before April 15, 2024. That extends your filing to October 15, 2024. There are no penalties for filing after the due date of the return if you are receiving a tax refund.
