Claude AI, developed by Anthropic, requires phone number verification to create an account, reset passwords, or enable two-factor authentication (2FA). However, many users encounter the error message: “Error sending code. Double check your phone number.”

This issue can prevent users from accessing Claude AI, delaying authentication and security verification. The error can stem from incorrect number entry, SMS delivery issues, or carrier restrictions. Below are practical solutions to resolve this problem.

Why Does Claude AI Show “Error Sending Code – Double Check Your Phone Number”?

Why Does Claude AI Show "Error Sending Code – Double Check Your Phone Number"?

This message means that Claude AI was unable to send an SMS verification code to your phone. The system uses SMS authentication to verify users, and any interruption in the process can cause the error.

Common reasons for this issue include:

Incorrect phone number format causing failed delivery.
Carrier restrictions blocking Claude AI messages.
Spam filters on the phone treating verification SMS as junk.
Claude AI system outage delaying code generation.
Too many verification attempts leading to a temporary block.

How to Fix Claude AI Phone Verification Error

Follow these steps to resolve the Claude AI phone verification issue and successfully receive your verification code.

1. Check Your Phone Number Format

One of the most common reasons for failed verification is incorrect number entry. Double-check that the number is entered correctly, including the country code.

For example:

Correct format for U.S. numbers: +1 555 123 4567
Incorrect format: 555-123-4567 (missing country code)

If the system does not allow re-entering the number, try clearing cache or switching devices before attempting again.

2. Restart Your Phone

Sometimes, network issues prevent SMS delivery. Restarting the device can refresh the connection to your mobile carrier’s network, allowing messages to come through.

Power off your phone completely.
Wait 30 seconds and turn it back on.
Retry the verification process in Claude AI.

3. Check Spam and Blocked Messages

Phone settings can filter or block SMS messages, preventing verification codes from being delivered.

Open your Messages app and check the Spam or Junk folder.
If Claude AI’s SMS is found there, mark it as Not Spam.
Check your blocked contacts list to ensure Claude AI’s number isn’t blocked.

If you recently installed a spam filtering app, try disabling it and retry the verification.

4. Disable VPN or Proxy Services

Some VPNs and proxies interfere with authentication servers, preventing SMS codes from being sent. If you are using a VPN or privacy-focused browser, disable it temporarily and retry the verification process.

5. Try a Different Network Connection

A poor internet connection or network filtering by your ISP can delay or block verification codes. If you’re on WiFi, try switching to mobile data or vice versa.

If using WiFi, switch to mobile data and retry verification.
If using mobile data, connect to a stable WiFi network and try again.

6. Wait and Retry Later

Too many failed attempts within a short period can temporarily block further code requests. Claude AI may have rate limits, restricting users from requesting codes too frequently.

Wait at least 15-30 minutes before retrying.
If the issue persists, try again after an hour.

7. Contact Your Mobile Carrier

Some mobile carriers block automated SMS messages, especially from international numbers. If Claude AI verification messages are not arriving, contact your carrier to check for blocked services.

Ask if automated verification messages are being blocked.
Request to whitelist Claude AI’s sender number.

If your carrier has strict SMS filtering, switching to a different phone number (on another carrier) may be necessary.

8. Use an Alternative Phone Number

If the verification code still isn’t received, try using another mobile number. Claude AI may restrict certain numbers or carriers, especially virtual numbers or VoIP services.

Avoid using VoIP numbers (e.g., Google Voice, Skype).
Try a different mobile provider’s number if available.

If an alternative number works, the issue may be carrier-related, requiring further action.

9. When to Contact Claude AI Support?

If none of the above solutions work, reaching out to Claude AI’s support team is the next step.

Provide details of the error message.
Mention what troubleshooting steps were attempted.
Include the phone number format and carrier details.

Claude AI’s support team may assist with manual verification or troubleshooting network issues.

Conclusion

The “Error sending code. Double check your phone number” issue in Claude AI is commonly caused by incorrect phone entry, blocked SMS, carrier restrictions, or network issues.

By checking number format, restarting the phone, disabling spam filters, and switching networks, most users can resolve the issue quickly. If problems persist, contacting Claude AI’s support team for manual assistance may be necessary.

If you have encountered this issue and found a working solution, share your experience in the comments to help others facing the same problem.

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Fix Error Sending Code – Double Check Your Phone Number in Claude AI

Why Does Claude AI Show “Error Sending Code – Double Check Your Phone Number”?