Vietnam SMS Best Practices, Compliance, and Features

Quick Answer: What You Need to Know About Vietnam SMS

To send SMS in Vietnam, you must register an alphanumeric sender ID (2–6 months processing time), comply with Decree 91/2020/ND-CP anti-spam regulations, and obtain explicit consent before sending marketing messages. Vietnam's three major operators—Viettel (56.3% market share), VNPT/Vinaphone (21%), and Mobifone (17.9%)—serve over 130 million subscribers. Send marketing SMS only between 7:00 AM – 10:00 PM GMT+7, include your registered brand name in all messages (mandatory since August 12, 2024), and respect the national Do Not Call registry. Penalties for violations range from VND 5–170 million (~$200–$6,800).

Vietnam SMS Market Overview

Market Conditions: Vietnam has a vibrant mobile market with high SMS usage alongside popular OTT (Over-The-Top) messaging apps. The country has three major mobile operators: Viettel (commanding 56.3% market share), VNPT/Vinaphone (21% market share), and Mobifone (17.9% market share), collectively serving over 130 million mobile subscribers as of 2024. Android devices dominate the market with approximately 65.7% market share, while iOS devices account for 33.7% (2024 data). While OTT apps like Zalo (Vietnam's leading messaging platform), Facebook Messenger, and WhatsApp are widely used, SMS remains crucial for business communications, especially for verification codes, notifications, and transactional messages. Source: Statista and GlobalData market reports, 2024.

Key SMS Features and Capabilities in Vietnam

Vietnam supports basic SMS features with strict regulations on sender IDs and content, requiring pre-registration for business messaging and maintaining specific compliance requirements for message delivery.

Two-way SMS Support

Two-way SMS is not supported in Vietnam for A2P (Application-to-Person) messaging. Use one-way messaging for your business communications, with no ability to receive replies from end users.

Concatenated Messages (Segmented SMS)

Support: Yes, concatenated messages are supported, though availability may vary based on sender ID type.
Message length rules: Messages are limited to 160 characters before splitting occurs (GSM-7 encoding). For concatenated messages, each segment is 153 characters (7 bytes reserved for UDH – User Data Header).

Encoding considerations:

• GSM-7 encoding: Used for standard ASCII characters (160 characters per segment, 153 per concatenated segment)
• UCS-2 encoding: Required for Vietnamese diacritical marks and special characters
  • Single message: 70 characters maximum
  • Concatenated message: 67 characters per segment
  • Important: Vietnamese diacritics (á, à, ả, ã, ạ, ă, ắ, ằ, ẳ, ẵ, ặ, â, ấ, ầ, ẩ, ẫ, ậ, etc.) are not included in the GSM-7 standard, so any message containing these characters will automatically trigger UCS-2 encoding, reducing capacity from 160 to 70 characters per segment
  • Vietnam uses up to 46 different character encodings for representing the Vietnamese alphabet

Best practice: For messages with Vietnamese diacritics, plan for 70-character segments to avoid unexpected message splitting and increased costs.

Sources: GSM 7-bit character set specification; Unicode Consortium; Twilio SMS Encoding Documentation.

MMS Support

MMS is not available in Vietnam. Any attempt to send MMS will fail, and it's recommended to send SMS with a URL link instead for sharing media content. However, note that messages containing URLs are subject to strict filtering and may face delivery challenges.

Recipient Phone Number Compatibility

Number Portability

Number portability is available in Vietnam. This means subscribers can change their mobile operator while keeping their phone number. While this doesn't significantly affect SMS delivery, maintain updated routing tables for optimal delivery rates.

Important: Always use E.164 phone number format (+84 followed by the subscriber number) when sending SMS to Vietnam through APIs. This international standard ensures proper call routing and compatibility across all telecommunications systems and SMS providers.

Sending SMS to Landlines

You cannot send SMS to landline numbers in Vietnam. Attempts to send messages to landline numbers will result in failed delivery and an error response (400 error code 21614 for Twilio's API). These messages won't appear in logs and won't incur charges.

Compliance and Regulatory Guidelines for SMS in Vietnam

Vietnam's SMS regulations are governed by the MIC (Ministry of Information and Communications) and the ABEI (Authority of Broadcasting and Electronic Information), with enforcement handled by the AIS (Authority of Information Security). Key regulations include Decree 91/2020/ND-CP (effective October 1, 2020), which replaced Decree 90/2008 and established comprehensive anti-spam measures, and the new Telecommunications Law (effective July 1, 2024), which introduced additional digital infrastructure and service provider requirements. Starting August 12, 2024, all SMS messages must include a brand name or application name in the message body that matches the registered alphanumeric Sender ID.

Regulatory Framework and Penalties

Decree 91/2020/ND-CP Anti-Spam Regulations:

• Effective date: October 1, 2020
• Scope: Spam SMS, emails, and calls
• Prior consent required (abolished previous opt-out regime)
• National Do Not Call registry mandatory

Administrative Penalties (Decree 91/2020):

• VND 5 – 10 million (~$200 – 400): Making advertising calls/SMS without clear prior consent
• VND 50 – 70 million (~$2,000 – 2,800): Using unregistered or unauthorized brand name
• VND 70 – 100 million (~$2,800 – 4,000): Using brand name for spam or illegal services
• VND 80 – 100 million (~$3,200 – 4,000): Sending to Do Not Call registry numbers
• VND 140 – 170 million (~$5,600 – 6,800): Failure to develop anti-spam systems or block DNC (Do Not Call) numbers
• Additional: Suspension of services for 1 – 3 months; confiscation of brand name usage rights for 1 – 3 months

Sources: Decree 91/2020/ND-CP; Vietnam Ministry of Information and Communications; Tilleke & Gibbins legal analysis, 2020.

Consent and Opt-In

Explicit Consent Requirements:

• Obtain written or electronic consent before sending any marketing messages
• Maintain consent records and make them readily available for audit
• Clearly state the purpose of messaging during opt-in
• Use double opt-in for marketing campaigns (recommended)

Best Practices for Consent Documentation:

• Store timestamp and source of consent
• Maintain detailed opt-in logs
• Keep records of consent for at least 2 years
• Document the specific services or message types the user agreed to receive

HELP/STOP and Other Commands

• Include opt-out information in Vietnamese in all messages
• Support standard keywords:
  • STOP, HUY, TD (Stop all messages)
  • HELP, HUONGDAN (Get help information)
• Send response messages in Vietnamese
• Send opt-out confirmations within 24 hours

Do Not Call / Do Not Disturb Registries

Vietnam maintains a national Do Not Call registry (Danh sách không quảng cáo) managed by the Authority of Information Security (AIS) under the Ministry of Information and Communications, as mandated by Decree 91/2020. Consumers can register their phone numbers to opt out of all advertising messages and calls. Businesses must:

• Check numbers against the DNC registry before sending messages
• Update their databases at least every 30 days
• Remove numbers from marketing lists within 24 hours of registration
• Maintain internal suppression lists for opt-outs
• Immediately cease sending to numbers upon opt-out request
• Respect frequency limits: Maximum 3 SMS messages per day and 1 call per day per recipient

Penalties: Sending to DNC registry numbers carries fines of VND 80 – 100 million (~$3,200 – 4,000).

Source: Decree 91/2020/ND-CP, Article 8 and Article 17.

Time Zone Sensitivity

Regulated Hours (Decree 91/2020):

• Marketing SMS: Permitted between 7:00 AM and 10:00 PM (GMT+7)
• Marketing calls: Restricted to 8:00 AM to 5:00 PM (GMT+7) unless recipient agrees otherwise
• Transactional messages can be sent 24/7
• Consider Vietnamese holidays and weekends for non-urgent communications

Note: Violations of time restrictions can result in administrative fines under Decree 91/2020.

Source: Decree 91/2020/ND-CP, Article 6.

Phone Numbers Options and SMS Sender Types in Vietnam

Alphanumeric Sender ID

Operator network capability: Fully supported and required for business messaging

Registration requirements:

• Pre-registration mandatory
• Processing time: 2 – 6 months from submission of complete documentation
• Must match business name or abbreviation from business license
• Cannot exceed 11 characters
• Allowed characters: a-z, A-Z, 0-9, and single space (no special characters)
• Dynamic usage not supported

Required Documents:

1. Business License: Color copy in English or Vietnamese (local or international)
2. Program Summary: Must include customer letterhead, message samples, opt-in process description; requires company signature and stamp
3. Brandname Registration Form: Must include business name and requested sender ID; requires signature and stamp
4. Content Template Registration Form: All message templates must be pre-approved
5. Company Stamp: All documents require official company stamp; submissions without stamps will be rejected

Important: SMS templates must always contain the registered Alphanumeric Sender ID. Carriers verify that the registering company owns the requested sender ID.

Sender ID preservation: Yes, registered Sender IDs are preserved across all major carriers

Sources: Twilio Vietnam Sender ID Registration Guide; 8x8 CPaaS Vietnam Documentation; Everbridge SMS Requirements, 2024.

Long Codes

Domestic vs. International:

• Domestic long codes not supported
• International long codes supported but not recommended

Sender ID preservation: No, international long codes are typically overwritten
Provisioning time: N/A
Use cases: Not recommended for business messaging in Vietnam

Short Codes

Support: Not currently supported in Vietnam
Provisioning time: N/A
Use cases: N/A

Restricted SMS Content, Industries, and Use Cases

Prohibited Content and Industries:

• Virtual currency and cryptocurrency
• Gambling and betting
• Adult content
• Political messages
• Religious content
• Controlled substances
• Cannabis
• Alcohol
• Firearms
• Unauthorized financial services

Financial Services Requirements:

• License from State Bank of Vietnam required
• Pre-approved message templates mandatory
• No promotional content allowed

Content Filtering

Carrier Filtering Rules:

• URLs and links typically blocked
• Phone numbers in message body not allowed
• WhatsApp/LINE chat links blocked
• Message content must match pre-approved templates

Tips to Avoid Blocking:

• Use registered Sender ID
• Follow approved message templates
• Include brand name in message body
• Avoid URL shorteners
• Keep content clear and straightforward

Best Practices for Sending SMS in Vietnam

Messaging Strategy

• Keep messages under 160 characters
• Include brand name at beginning of message
• Use clear call-to-actions
• Avoid promotional language in transactional messages

Sending Frequency and Timing

• Limit to 1 – 2 messages per day per recipient
• Respect quiet hours (8 PM – 8 AM)
• Avoid sending during Tet Holiday period
• Space out bulk campaigns to prevent network congestion

Localization

• Use Vietnamese as your primary language
• Include proper Vietnamese diacritical marks
• Consider including English translation for international businesses
• Follow local date/time formats (DD/MM/YYYY)

Opt-Out Management

• Process opt-outs within 24 hours
• Maintain centralized opt-out database
• Send opt-out confirmation
• Conduct regular audits of opt-out lists

Testing and Monitoring

• Test across all major carriers (Viettel, Vinaphone, Mobifone)
• Monitor delivery rates by carrier
• Track opt-out rates
• Conduct regular content compliance checks
• Test message rendering on popular device types

SMS API integrations for Vietnam

Twilio

Twilio provides a RESTful API (Application Programming Interface) for sending SMS messages to Vietnam. Authentication uses account SID (Security Identifier) and auth token.

import { Twilio } from "twilio";

// Initialize client with your credentials
const client = new Twilio(
  process.env.TWILIO_ACCOUNT_SID,
  process.env.TWILIO_AUTH_TOKEN
);

async function sendSMSToVietnam() {
  try {
    // Send message with required brand name prefix
    const message = await client.messages.create({
      body: "[YourBrand] Your verification code is: 123456",
      from: "YOUR_REGISTERED_SENDER_ID", // Must be pre-registered
      to: "+84123456789", // Vietnam number in E.164 format
      // Optional parameters for delivery tracking
      statusCallback: "https://your-callback-url.com/status"
    });
    
    console.log(`Message sent with SID: ${message.sid}`);
    return message;
  } catch (error) {
    console.error("Error sending message:", error);
    throw error;
  }
}

Sinch

Sinch requires API token authentication and supports batch sending capabilities.

import axios from "axios";

const SINCH_API_TOKEN = process.env.SINCH_API_TOKEN;
const SINCH_SERVICE_PLAN_ID = process.env.SINCH_SERVICE_PLAN_ID;

async function sendBatchSMS() {
  const url = `https://sms.api.sinch.com/xms/v1/${SINCH_SERVICE_PLAN_ID}/batches`;
  
  try {
    const response = await axios.post(url, {
      from: "YOUR_SENDER_ID",
      to: ["+84123456789"],
      body: "[YourBrand] Your message here",
      delivery_report: "summary"
    }, {
      headers: {
        "Authorization": `Bearer ${SINCH_API_TOKEN}`,
        "Content-Type": "application/json"
      }
    });
    
    console.log("Batch ID:", response.data.id);
    return response.data;
  } catch (error) {
    console.error("Sinch API error:", error.response?.data);
    throw error;
  }
}

Bird

Bird CRM's API requires workspace and channel setup before sending messages.

import axios from "axios";

interface BirdSMSResponse {
  messageId: string;
  status: string;
}

async function sendBirdSMS(
  phoneNumber: string,
  message: string
): Promise<BirdSMSResponse&gt; {
  const BIRD_API_KEY = process.env.BIRD_API_KEY;
  const WORKSPACE_ID = process.env.BIRD_WORKSPACE_ID;
  const CHANNEL_ID = process.env.BIRD_CHANNEL_ID;

  try {
    const response = await axios.post(
      `https://api.bird.com/workspaces/${WORKSPACE_ID}/channels/${CHANNEL_ID}/messages`,
      {
        receiver: {
          contacts: [{ identifierValue: phoneNumber }]
        },
        body: {
          type: "text",
          text: { text: `[YourBrand] ${message}` }
        }
      },
      {
        headers: {
          "Authorization": `AccessKey ${BIRD_API_KEY}`,
          "Content-Type": "application/json"
        }
      }
    );
    
    return response.data;
  } catch (error) {
    console.error("Bird API error:", error);
    throw error;
  }
}

API Rate Limits and Throughput

Vietnam carriers impose various rate limits:

• Maximum 30 messages per second per sender ID
• Daily volume limits vary by carrier
• Batch processing recommended for large campaigns

Throughput Management Strategies:

• Implement exponential backoff for retries
• Use queuing systems (Redis, RabbitMQ) for high volume
• Schedule campaigns across multiple time windows
• Monitor carrier feedback for throttling

Error Handling and Reporting

Common Error Scenarios:

• Invalid sender ID (401/403)
• Message content violations (400)
• Network timeouts (504)
• Rate limiting (429)

Logging Best Practices:

interface SMSLogEntry {
  messageId: string;
  timestamp: Date;
  recipient: string;
  status: string;
  errorCode?: string;
  retryCount: number;
}

async function logSMSActivity(entry: SMSLogEntry): Promise<void&gt; {
  // Implement logging to your preferred system
  // Consider using structured logging tools like Winston
  console.log(JSON.stringify(entry));
}

Frequently Asked Questions About Vietnam SMS

What are the SMS regulations in Vietnam for 2024?

SMS communications in Vietnam are regulated by the Ministry of Information and Communications (MIC), with enforcement by the Authority of Information Security (AIS). The primary legal framework is Decree 91/2020/ND-CP (effective October 1, 2020), which requires explicit written or electronic consent before sending marketing messages, mandates a national Do Not Call registry, and establishes penalties ranging from VND 5–170 million (~$200–$6,800). The new Telecommunications Law (effective July 1, 2024) introduced additional requirements. Since August 12, 2024, all SMS messages must include a brand name or application name matching your registered alphanumeric Sender ID.

How long does sender ID registration take in Vietnam?

Sender ID registration in Vietnam requires 2–6 months from submission of complete documentation. You must provide a business license (color copy in English or Vietnamese), program summary with message samples and opt-in process description, brandname registration form, content template registration form, and official company stamp on all documents. Your sender ID must match your business name or abbreviation, cannot exceed 11 characters, and may only contain a-z, A-Z, 0-9, and single space. Dynamic sender IDs are not supported.

What are the penalties for violating Vietnam SMS regulations?

Decree 91/2020/ND-CP establishes administrative penalties: VND 5–10 million ($200–400) for sending advertising SMS without clear prior consent; VND 50–70 million ($2,000–2,800) for using unregistered or unauthorized brand names; VND 70–100 million ($2,800–4,000) for using brand names for spam or illegal services; VND 80–100 million ($3,200–4,000) for sending to Do Not Call registry numbers; and VND 140–170 million (~$5,600–6,800) for failing to develop anti-spam systems or block DNC numbers. Additional penalties include service suspension and confiscation of brand name usage rights for 1–3 months.

Which mobile operators dominate Vietnam's SMS market?

Vietnam's mobile market is dominated by three operators serving over 130 million subscribers: Viettel (56.3% market share), VNPT/Vinaphone (21% market share), and Mobifone (17.9% market share). Android devices dominate with 65.7% market share, while iOS accounts for 33.7% (2024 data). While OTT apps like Zalo, Facebook Messenger, and WhatsApp are popular, SMS remains crucial for business communications, particularly verification codes, notifications, and transactional messages.

Does Vietnam support two-way SMS messaging?

No, two-way SMS is not supported in Vietnam for A2P (Application-to-Person) messaging. Use one-way messaging for your business communications, with no ability to receive replies from end users. This limitation affects interactive applications like customer service chatbots or survey responses. For use cases requiring two-way communication, consider alternative channels like voice calls or OTT messaging apps.

How do Vietnamese diacritical marks affect SMS character limits?

Vietnamese diacritics (á, à, ả, ã, ạ, ă, ắ, ằ, ẳ, ẵ, ặ, â, ấ, ầ, ẩ, ẫ, ậ, etc.) are not included in the GSM-7 standard, so any message containing these characters automatically triggers UCS-2 encoding. This reduces capacity from 160 characters (GSM-7 single message) to 70 characters (UCS-2 single message), and from 153 characters per concatenated segment to 67 characters per concatenated segment. Vietnam uses up to 46 different character encodings for representing the Vietnamese alphabet. Plan for 70-character segments when including Vietnamese diacritics to avoid unexpected message splitting and increased costs.

What are the time restrictions for sending SMS in Vietnam?

Decree 91/2020/ND-CP restricts marketing SMS to 7:00 AM – 10:00 PM GMT+7, while marketing calls are limited to 8:00 AM – 5:00 PM GMT+7 unless the recipient agrees otherwise. Transactional messages can be sent 24/7. Consider Vietnamese holidays and weekends for non-urgent communications. Violations of time restrictions result in administrative fines under Decree 91/2020.

What is the national Do Not Call registry in Vietnam?

Vietnam maintains a national Do Not Call registry (Danh sách không quảng cáo) managed by the Authority of Information Security (AIS) under the Ministry of Information and Communications, as mandated by Decree 91/2020. Consumers can register their phone numbers to opt out of all advertising messages and calls. You must check numbers against the DNC registry before sending messages, update your databases at least every 30 days, remove numbers from marketing lists within 24 hours of registration, and respect frequency limits: maximum 3 SMS messages per day and 1 call per day per recipient. Sending to DNC registry numbers carries fines of VND 80–100 million (~$3,200–4,000).

Which SMS API providers support Vietnam?

Major SMS API providers supporting Vietnam include Twilio (RESTful API with account SID and auth token authentication), Sinch (API token authentication with batch sending capabilities), and Bird CRM (workspace and channel setup required). Vietnam carriers impose rate limits of maximum 30 messages per second per sender ID, with daily volume limits varying by carrier. Implement exponential backoff for retries, use queuing systems (Redis, RabbitMQ) for high volume, and monitor carrier feedback for throttling. All providers require E.164 phone number formatting (+84 country code) and support status callbacks for delivery tracking.

What content is restricted for SMS in Vietnam?

Prohibited content includes virtual currency and cryptocurrency, gambling and betting, adult content, political messages, religious content, controlled substances, cannabis, alcohol, firearms, and unauthorized financial services. For financial services, you need a license from the State Bank of Vietnam, pre-approved message templates, and no promotional content allowed. Carrier filtering rules typically block URLs and links, phone numbers in message body, and WhatsApp/LINE chat links. Message content must match pre-approved templates. To avoid blocking, use registered Sender IDs, follow approved message templates, include brand name in message body, avoid URL shorteners, and keep content clear and straightforward.

Recap and Additional Resources

Key Takeaways

1. Compliance Requirements:

   • Brand name inclusion mandatory
   • Pre-registered sender IDs required
   • Strict content restrictions

2. Technical Considerations:

   • E.164 number formatting
   • Message template compliance
   • Rate limit management

3. Best Practices:

   • Vietnamese language support
   • Proper opt-out handling
   • Delivery time restrictions

Next Steps

1. Regulatory Compliance:

   • Review MIC guidelines
   • Register sender IDs
   • Prepare message templates

2. Technical Setup:

   • Choose API provider
   • Implement error handling
   • Set up monitoring

3. Testing:

   • Verify delivery across carriers
   • Test opt-out workflow
   • Monitor delivery rates

Additional Resources

Official Resources:

• Ministry of Information and Communications (MIC): https://www.mic.gov.vn
• Vietnam Telecommunications Authority: https://vnta.gov.vn

Industry Guidelines:

• Vietnam Mobile Marketing Association
• GSMA (GSM Association) Guidelines for Vietnam

API Provider Documentation:

• Twilio Vietnam Guidelines
• Sinch Vietnam API Documentation
• Bird CRM Integration Guide

Related Guides:

• Thailand SMS Guide – SMS regulations and pricing for neighboring Thailand
• Singapore SMS Guide – SMS compliance in Singapore
• 10DLC SMS Registration – US A2P 10DLC campaign registration for international businesses