You enter your phone number, get an SMS code, enter it, and instead of finishing signup, ChatGPT says “this number is already in use” or simply throws you back to the phone-entry screen. The loop is almost always a number-reuse policy, a virtual / VOIP number being blocked, or a carrier that does not deliver to OpenAI’s SMS provider. The shortest path: confirm the number is real-mobile and never used for ChatGPT before, then try once more from a clean session. Skip VPN.
Common causes
1. Number was already used to verify another ChatGPT account
OpenAI enforces one ChatGPT signup per phone number — likely lifetime. If you ever signed up before (Free or Plus, with a now-deleted account), that number is permanently bound.
How to judge: Try to log in with the number’s associated email — if it works, that account already exists. If you no longer have access, recovery has to happen via help.openai.com first.
2. VOIP / virtual number rejected
Google Voice, TextNow, Twilio, second-line apps, and some MVNO numbers are flagged as VOIP and rejected. The signup form sometimes accepts them initially then rejects after code entry.
How to judge: Run the number through any “carrier lookup” tool — type returned as “VOIP” or “Wireless Reseller” → almost certainly rejected.
3. Region blocked or not on OpenAI’s SMS list
Some country codes (sanctioned regions, or low-deliverability ones) cannot complete SMS verification. The code may never arrive, or the entered code may always be rejected.
How to judge: You never receive the SMS at all even after several minutes, or the same correct code is rejected repeatedly.
4. Carrier delivery delay; code expired by the time it arrived
Some carriers delay SMS by 5-15 minutes. The 6-digit code expires in ~10 minutes, so when you finally enter it, ChatGPT rejects it as expired and asks for a new code — feels like a loop.
How to judge: Look at the SMS timestamp vs when you entered it. Over 10 minutes between send and entry = expiry.
5. Browser cache / partial signup record
If a previous signup attempt half-completed (email verified, phone failed), the next attempt may pull stale state from cookies and skip steps, then loop.
How to judge: Clear cookies and try in an incognito window. Loop disappears = cache state.
Before you start
- Use a real mobile number on a major carrier (AT&T, Verizon, T-Mobile, Vodafone, etc.). Do not start with a VOIP number.
- Turn off VPN, especially if it changes country. SMS verification is region-sensitive.
- Have the phone in your hand and signal verified — not in another room or on Wi-Fi calling only.
Information to collect
- Exact error message and the screen where it appeared.
- Country code and carrier of the phone number.
- Whether the number is postpaid, prepaid, or VOIP.
- Time between SMS receipt and code entry.
- Browser, OS, and whether using incognito.
- Whether you have ever signed up for ChatGPT before with this number or email.
- Whether you can receive SMS from other services (banking, Google) without delay.
Step-by-step fix
Step 1: Test SMS deliverability with another service
Before blaming OpenAI, send yourself a test SMS via Google’s password reset, your bank’s 2FA, or any other service. Arrived in under 30 seconds? Carrier is fine. Took 5+ minutes or never arrived? Carrier delivery is the problem — try a different number.
Step 2: Clear all OpenAI-related cookies and start fresh
In an incognito / private window, or after clearing chatgpt.com + openai.com + auth.openai.com cookies. Go to chatgpt.com → Sign up. Enter email and password (or SSO), receive email verification, click the link, then phone screen.
Step 3: Enter the number in international format
Always use +CountryCode NumberWithoutLeadingZero:
US: +1 5551234567
UK: +44 7700900123
Germany: +49 17612345678
India: +91 9876543210
China: +86 13800138000 (note: mainland numbers historically blocked)Missing the + or dropping the country code causes silent rejection.
Step 4: Enter the code within 5 minutes
The moment SMS arrives, switch back to the browser and enter immediately. If you typed slowly and got the loop, request a new code and prioritize speed over accuracy on the first try.
If the code never arrives within 5 minutes, click “Resend” exactly once and wait another 5. More than two resends often results in a 24-hour rate limit on that number.
Step 5: If VOIP / virtual, switch numbers
OpenAI’s VOIP filter is strict. If your number is Google Voice / TextNow / Twilio, you have three options:
- Borrow a friend’s real mobile number for verification (the number is bound to that account thereafter — they cannot use it for their own ChatGPT later)
- Buy a prepaid SIM in a supported country
- Wait for OpenAI to update VOIP policy (not reliable)
Currently no software workaround exists.
Step 6: For region blocks, do not use VPN to fake region
A VPN changes your IP but cannot change the country code of the phone number. SMS verification looks at the number’s country, not your IP. Using VPN may actually trigger additional anti-fraud checks. Use a real number from an unblocked country instead.
Step 7: If the number is “already in use” and you do not know the account
Go to help.openai.com → “I cannot access my account” → describe: “Phone number +1 555… is reported as in use, but I do not have access to the associated account.” Submit. They will either help recover the original account or release the number after identity verification (slow, 7-14 days).
Verify
- After entering the SMS code, the page advances to the avatar / name screen (not back to phone entry).
- chatgpt.com loads the chat interface with your fresh account email shown top-right.
- Settings → Account shows the verified phone number listed.
- An “Account created” confirmation email is in your inbox.
- You can sign out and back in without re-verification.
Long-term prevention
- Sign up with a real, primary mobile number — not a burner or VOIP — to avoid future verification headaches.
- If you might want multiple ChatGPT accounts later (work, personal), use separate real numbers for each from day one.
- Do not delete an account whose phone you might want to reuse — OpenAI does not necessarily release the number on deletion.
- For corporate signups, use a dedicated company phone or your work mobile, not a personal cell that you may later use for personal account.
- Save the recovery email separately from the signup email so future verification flows have an alternative.
Common pitfalls
- Hitting “Resend” rapidly hoping a code arrives — triggers rate limits that lock the number for 24 hours.
- Entering the number without country code — the form often accepts but verification fails silently.
- Using VPN during signup — extra anti-fraud checks make verification harder, not easier.
- Trying to reuse a number from a deleted account — the binding persists even after deletion.
- Switching browser or tab while waiting for the code — the original verification session expires.
FAQ
Q: Why is my phone number “already in use” if I never had ChatGPT? A: Likely a family member or coworker used your number on their account, or you signed up briefly and forgot. Recover via help.openai.com.
Q: Can I skip phone verification entirely? A: No. Phone verification is required for all new ChatGPT accounts and most API account creation flows.
Q: How many ChatGPT accounts can one phone number have? A: One. The binding is essentially permanent.
Q: Does deleting my account release the phone number? A: Officially yes, in practice often no — OpenAI retains anti-abuse signals on the number for an extended period.
Q: Is there a way to sign up with email only? A: Not currently. Some legacy accounts pre-date the phone requirement, but new signups require it.