The US country code is +1. When you need to format an international phone number to reach a United States subscriber or receive an SMS verification code from a US-based platform, you prefix the local number with +1 followed by the 10-digit subscriber number.
Getting your head around the North American Numbering Plan can get tricky if you are dialing from overseas or trying to troubleshoot a failed one-time password (OTP) or two-factor authentication (2FA) prompt. Carrier filters, area codes, and number types all play a role in whether your text message arrives or vanishes in transit.
Quick answer
The US country code is +1. To format any US phone number for international dialing or API integration, use the structure +1-XXX-XXX-XXXX, where the middle three digits represent the area code and the final four digits form the subscriber line number.
Understanding the North American Numbering Plan
Unlike many countries where mobile numbers and landline numbers use entirely different dialing prefixes, the United States shares a unified numbering pool under country code +1. This pool also covers Canada and several Caribbean nations. Because of this shared space, you cannot tell if a number is mobile or fixed simply by looking at the country code.
A standard US phone number always contains ten digits after the +1 country code. The first three digits form the area code, known as the NPA. Next come the three digits of the central office code, and finally the four-digit line number. When you input a number into an app's verification field, drop any leading zero or domestic trunk prefix like 1 from the start of the local string if you are including the international country code, though many modern web forms handle this automatically.
Common US Formatting Mistakes During SMS Verification
When users fail to receive an OTP code from services like Google, OpenAI, or local US banks, formatting is usually the culprit. Automated systems are strict about string lengths.
If you leave the domestic prefix on the front of the local number while also selecting the US country code from a dropdown menu, the system might try to dial +11 followed by the area code. That extra digit invalidates the route, and the message fails to leave the gateway. Another frequent error is including parentheses and hyphens in rigid API fields that only accept raw integer strings.
Carriers also enforce strict rules on message delivery speeds. T-Mobile and Verizon short-code filters occasionally drop OTPs from unregistered senders about two seconds after arrival if the sending gateway has a low sender score. You might see the system report that a code was sent, but your device stays silent.
Mobile vs. VoIP Numbers for Verification
Platform security teams look closely at the underlying carrier type when you register a new account. Traditional mobile numbers tied to a SIM card on major networks like AT&T or T-Mobile rarely face verification blocks.
On the other hand, Voice over Internet Protocol (VoIP) numbers routed through software applications face aggressive filtering on platforms like WhatsApp, Telegram, and financial apps. Many services maintain blacklists of known VoIP prefixes to prevent mass account creation and bot activity. For users who need a private option instead of a public inbox, Codesverify offers rental numbers for many countries and apps, though availability varies depending on current carrier inventory.
Frequently Asked Questions
What is the country code for the United States?
The country code for the United States is +1. It is shared with Canada and several islands in the Caribbean region under the North American Numbering Plan.
Do I need to dial 1 before a US phone number?
If you are calling or sending an SMS from within the US or Canada, you dial 1 followed by the 10-digit number for long-distance calls. If you are dialing from outside North America, you use the international format starting with +1.
Why is my US SMS verification code not arriving?
Delivery failures usually happen because of carrier filtering, incorrect international formatting, or the platform blocking the specific number range. Trying a non-VoIP number often resolves the issue.
Are Canadian numbers part of the US country code?
Yes. Canada shares the +1 country code with the US. Area codes determine whether the destination is in the US or Canada.
How many digits are in a US phone number after the country code?
There are exactly 10 digits after the +1 country code, split into a 3-digit area code and a 7-digit subscriber number.
Can I use a US virtual number for banking verification?
Most major banks require a physical mobile number tied to a major carrier and reject virtual or temporary numbers for security compliance.
Related guides
- Phone Extension for USA: Country Code & SMS Guide (2026)
- Country Code for the USA: Format & SMS Verification Guide