Free answer
Your baby's Social Security number
Federal
You need it for taxes, for insurance and for most accounts. The easy route is to apply at the hospital as part of registering the birth — it takes a checkbox and a signature, and skipping it means doing the whole thing yourself later.
What people get wrong
- The hospital does not always ask clearly. If nobody mentioned it, assume it was not done and check.
- The number arrives by mail some weeks later. That is normal.
Where this comes from
Checked against these sources on 2026-10-12. Rules change — if a deadline matters to you, confirm it with the authority rather than with us.
Knowing it and doing it are different jobs
That’s the answer, in full, and it costs nothing. FIRST YEAR, FIGURED OUT. is the part that remembers it for you: this and 6 other admin topics as an ordered checklist, built around your due date, ticked off as you go, alongside the roadmap, the tracker and the 3 a.m. guides.