A reference to the Social Security cards needed by any child you claim as a dependent on your tax return. The nine-digit identifying number shown on the card must be reported on the tax return of the parent who claims the child as a dependent. What if a child is born late in the year and you haven’t received a Social Security number by the time you’re ready to file? The IRS says you must delay filing, even if it means getting an extension to file past the April 15 deadline. If you claim a dependent and fail to include the number, the exemption will be rejected and your tax bill hiked accordingly.