Keeping a US phone number after you leave: the 2FA problem nobody warns you about
The short version. When you leave the US, your US SIM eventually stops working — and with it, every text-message login code (2FA) tied to that number. That quietly locks you out of banks, brokerages, and credit cards at the worst possible time. The fix is cheap and boring: keep one real US phone number alive before you go. VoIP (like Google Voice) helps but gets rejected by some banks, so a low-cost real number is the safer anchor. This is the one piece of admin I’d tell anyone leaving the US to handle first.
I’m a Japanese national who spent four years working in the US, and I researched this while planning my move back to Japan. Of all the money-side problems of leaving — brokerages, taxes, cards — this is the one that’s the cheapest to solve and the most painful to ignore. Because it doesn’t fail on the day you leave. It fails three months later, when you try to log in and the code never arrives.
Why your logins break when the number dies
Most US financial institutions send your two-factor authentication (2FA) code by SMS text to a US mobile number. That’s fine while you’re in the US. But once you cancel your US carrier — or your prepaid SIM lapses — that number goes dead, and:
- The login code has nowhere to land.
- Many US banks won’t text a foreign number at all.
- Some services are US-only and won’t even show a foreign number as an option.
So the account might be perfectly fine. You just can’t get in. And you often can’t fix it remotely, because resetting the number itself requires… a code sent to the old number.
What actually breaks
It’s broader than you’d think. The same dead-number problem hits:
- Brokerages — Schwab, Fidelity, Vanguard, etc. (SMS 2FA on login)
- Credit cards — logging in, approving charges, fraud alerts
- Banks — transfers, wires, password resets
- The IRS / tax software — identity verification
- Payment apps — PayPal, Venmo, Zelle
- Old 401(k) / HSA portals — often the strictest
If you’re keeping any US financial relationship after you leave — and most people do — you need a US number that stays reachable.
The options, side by side
| Option | Monthly | What it does | Watch out for |
|---|---|---|---|
| Tello (MVNO) | ~$5 | A real US mobile number on a major US network; SMS 2FA arrives reliably | Paid; a small monthly cost |
| Google Voice | Free | Keeps a US number, forwards texts | Must be set up before you leave (you can’t get one from abroad); it’s VoIP, and some banks reject VoIP for 2FA |
| Keep your old carrier | $$$ | Simplest — just don’t cancel | Expensive for a number you barely use; some plans lapse if unused abroad |
| Foreign SIM only | — | Your new local number | US banks often won’t text it; not a solution on its own |
Why “just use Google Voice” isn’t the whole answer
Google Voice is genuinely useful, and free — but two catches keep it from being a complete fix:
- You have to set it up before you leave. You can’t create a Google Voice number from outside the US, and porting a number in also has to happen while you’re stateside.
- It’s VoIP, and some institutions block VoIP numbers for 2FA. Which ones? That isn’t published, so it’s a guess until you test it — and you don’t want to discover the block when you’re already locked out.
The safe posture is belt and suspenders: keep Google Voice if you like (great for calls and general texts), but also keep one real US number as the anchor for anything financial.
Why a real number, not just VoIP
Banks increasingly try to detect VoIP numbers and treat them as higher-risk, precisely because they’re easy to spin up for fraud. A number that runs on a real US mobile network doesn’t trip that filter. That’s the whole reason I’d pay a few dollars a month: it’s the difference between “my 2FA works everywhere” and “it works until the one time it really matters.”
Tello is the low-cost option I’d point people to here — it’s a US MVNO running on a major carrier’s network, plans start around $5/month, and you can go as bare-bones as a tiny data allotment since all you really need is to receive texts and the occasional call. Set it up while you still have a US address and card on file, and your login lifeline is handled.
(Full disclosure: the Tello links here are a referral link — you and I each get $10 in Tello credit if you sign up through it. I mention Tello because it’s the exact option I’d use for keeping a US number after leaving.)
What to do before you leave — a short checklist
- Pick your anchor number. A cheap real US number (Tello or similar). Optionally add Google Voice for general use.
- Set it up while you’re still in the US (US address + US card make signup painless).
- Update 2FA on every financial account to that number — one by one, before you fly.
- Test it. Log out and back into your bank/brokerage and confirm the code arrives.
- Keep it funded. A lapsed number is the same as no number — set autopay.
Do this before you go and you skip the worst-case scramble: locked out of your own accounts, on the wrong side of the ocean, needing a code that only a dead number can receive.
FAQ
Can’t I just use my new local (foreign) phone number?
Usually not for US financial logins. Many US banks won’t send 2FA texts to a foreign number at all, and some won’t accept one as a 2FA method. Keep a US number as the anchor for anything financial.
Is Google Voice enough on its own?
It can work, but two caveats: you must set it up before leaving the US, and it’s VoIP, which some banks reject for 2FA. Many people keep Google Voice and one real US number so there’s always a fallback.
How cheap can I go?
Since you mainly need to receive texts and occasional calls, the smallest plan is usually fine. Low-cost MVNOs like Tello start around $5/month, which is cheap insurance against being locked out of your accounts.
Does this matter if I’m keeping my US credit cards or brokerage?
Yes — those are exactly the accounts that use SMS 2FA. If you’re keeping any US financial relationship after you move, the phone number is what keeps you able to actually log in.