SMS Sender ID: Supported Characters, Rules & Best Practices

An SMS Sender ID is the name displayed on a recipient’s mobile phone when an SMS is sent. Instead of displaying a long phone number, a business can use a recognizable Sender ID such as:

Text.lk, PizzaHut, Daraz, SingerSL

For businesses and organizations using Text.lk, choosing the right Sender ID helps maintain consistent brand recognition and improves the professionalism of customer communications.

What is an SMS Sender ID?

An SMS Sender ID is the name shown in the recipient’s SMS as the sender. Text.lk supports an alphanumeric Sender ID, with limited to 11 characters. Instead of traditional phone number, customer / recipient seeing alphanumeric Sender ID.

For example, instead of the customer seeing:

0771234567

they can see:

ABCStore

or:

ABC Store

The Sender ID is useful for:

• OTP messages
• Login/security alerts
• Order notifications
• Delivery updates
• Promotional SMS
• Banking/payment notifications
• Appointment reminders
• Business communications

An SMS Sender ID is a way to identify your company or brand in the SMS “From” field. 

Read More: What is an SMS Sender ID?

What are the Sender ID requirements when sending SMS to recipients in Sri Lanka (+94)?

1. Organisations are encouraged to use their brand names as part of AlphaNumeric Sender IDs.
2. SMSs sent using Generic Sender IDs, including any variations of these (capitalised, lowercase or a combination) will be blocked. E.g, ALERT, Info, PassCode, etc

How many characters can a Sender ID have?

The most important restriction is: a maximum of 11 characters for an alphanumeric Sender ID. Spaces count toward the limit.

For example:

Spaces count toward the 11-character limit.

Which characters are supported for SMS Sender ID?

Text.lk’s Sender ID guidance specifically recommends:

Best Sender ID examples

Generally acceptable / recommended

A-Z
a-z
0-9
␣ (space)
. (dot)
- (hyphen)
_ (underscore)

For example:

ABCStore
ABC Store
ABC-Store
ABC_Store
ABCStore.lk
ABC24

Text.lk specifically lists letters, numbers, spaces, dots, hyphens, and underscores as allowed/recommended Sender ID characters.

Characters you should avoid

# % $ * = / \ ! ? : ; , ( ) [ ] { } < > | ^ ~ ` “

Text.lk’s Sender ID guidance specifically advises avoiding special characters such as #, @, %, $, etc.

Best SMS Sender ID format for Text.lk

For a business, we recommend this format:

MyBis

Or, if necessary:

My Bis
My-Bis
My_Bis
MyBisLK
MyBis.lk
MyBis1

Bad choices:

MyBisSriLanka (11-character limit exceeded)

For example, if your company is Lanka Electronics:

Good choices:

LankaElec
Lanka Elec
Lanka-EL
Lanka_EL
LankaElec1
LankaEl.lk

Bad choices:

Lanka@Elec
Lanka#Elec
Lanka$Elec
Lanka!Elec
Lanka&Elec
LankaElec.lk (11-character limit exceeded)

The safest approach is to keep the Sender ID simple, recognizable, and brand-related. Text.lk itself recommends keeping Sender IDs short and memorable and generally avoiding special characters.

Can I use numbers in an SMS Sender ID?

Yes, numbers can be part of an alphanumeric Sender ID according to Text.lk’s guidance.

Alphanumeric Sender IDs must contain at least one letter.

Examples:

ABC24
Shop24
MyBrand1
Brand2026

However, Text.lk advises against using numbers-only Sender IDs for branding, because they are less recognizable as a business identity.

So:

ABC24 (Fine ✅)
Shop24 (Fine✅)
2024 (⚠️ Not recommended for branding)
123456 (⚠️ Not recommended)

Can I use spaces in an SMS Sender ID?

Text.lk’s Sender ID guidance lists spaces among the allowed characters. 

For example:

ABC Store
My Shop
Lanka Bank
ABC Travel

But remember, a space is counted as a single character.

Can I use a hyphen (-) in an SMS Sender ID?

Yes. Text.lk’s guidance lists the hyphen as an allowed character.

Examples:

ABC-Store
My-Shop
ABC-24
Lanka-EL

This can be useful when your preferred brand name doesn’t fit nicely without separation.

Can I use an underscore (_) in an SMS Sender ID?

Yes. Text.lk’s guidance lists underscore as an allowed character.

Examples:

ABC_Store
My_Shop
ABC_24

However, for customer-facing SMS, we would generally prefer:

ABC Store

or:

ABC-Store

over:

ABC_Store

because the former looks more natural to recipients.

Can I use the At Sign (@) in an SMS Sender ID?

You can use @ in a live Sender ID. But need strict verification to use the @ sign in a sender ID. Even if a text.lk accept Sender ID including @ sign, sometimes telecom networks will block it.

• Why? Telecom operators and compliance bodies globally restrict @ because it mimics social media handles or email addresses, making it a high-risk tool for phishing scams and fraud.
• Providers like Whispir and Brevo explicitly list @ under their “Strictly Prohibited” rules; messages containing it face mandatory blocking.

Can I use an & in an SMS Sender ID?

Yes. The period character (&) can be used, but is not supported in all countries

ABC&Co
P&S

Can I use a hash symbol (#) in an SMS Sender ID?

You can use # (hash symbols), but it will cause your text messages to fail and get filtered as spam by the recipient carrier. Stick to letters and numbers for your brand name.

Can I use a dot / period character (.) in an SMS Sender ID?

Yes. The period character (.) can be used, but is not supported in all countries.

Also, sender IDs with the period character (.) must complete domain verification for Sender ID approval.

Examples:

Text.lk
MyBis.lk
ABC.Store

Can I use a plus (+) in an SMS Sender ID?

Yes. The plus symbol (+) can be used, but is not supported in all countries.

Examples:

A+ Econ
Motor+

Can I use emojis in an SMS Sender ID?

Don’t use emojis in your Sender ID.

For example, avoid:

ABCStore 😊
❤️ABC

Use a conventional alphanumeric business name instead.

What about Sinhala or Tamil characters?

No, you cannot use Unicode characters (such as non-Latin alphabets like Sinhala, Tamil, Arabic, or Chinese, or emojis) in an SMS Sender ID.

While Text.lk SMS gateway fully supports Unicode inside the body of a text message, the Sender ID itself is strictly limited.

Therefore, we would not assume that Sinhala or Tamil Unicode characters are supported in the Sender ID simply because Text.lk supports Sinhala/Tamil text inside SMS messages.

For example, don’t assume that:

ලංකා
தமிழ்

Sender ID vs SMS message characters

This is extremely important.

Sender ID and SMS message content are two different things, and their character rules should not be treated as identical. A Sender ID is the name shown as the sender, such as ABCStore, while the SMS message is the actual text sent to the recipient, such as “Your ABC Store OTP is 482931. Do not share this with anyone.”

For SMS message bodies, Text.lk explains that messages can use GSM-7, GSM-7 Extension, or UTF-16 encoding. Certain characters require additional GSM encoding space and can affect the number of characters that fit into an SMS. These encoding rules apply to the message body and should not automatically be assumed to apply to the Sender ID.

The 11-character rule

When designing a Sender ID, count every character.

For example:

ABC-Store

Count:

A B C - S t o r e
1 2 3 4 5 6 7 8 9

So it is 9 characters.

Text.lk’s API documentation explicitly states that an alphanumeric Sender ID can have a maximum length of 11 characters.

Sender ID approval

You cannot simply choose any Sender ID and assume that it can be used for production.

In Text.lk you can request a Sender ID from the Sender ID section under in the dashboard.

Text.lk’s Sender ID request guide says you need to provide authorization information, including the Sender ID, company name and business registration/NIC information as applicable.

Text.lk — How to Request a Sender ID

How long does approval take?

Text.lk currently says Sender ID approval usually takes:

A few hours to 1 business day

but in some cases:

up to 3 business days.

Text.lk also says fast-track approval can be requested at no additional cost.

So don’t design your production system assuming a new Sender ID becomes active immediately.

Don’t use TextLKDemo in production

Text.lk provides TextLKDemo for testing.

However, Text.lk explicitly says that TextLKDemo is strictly for testing and must not be used for OTPs or production-related messages. Using TextLKDemo for production can result in account suspension. 

For production:

❌ TextLKDemo

Use:

✅ Your approved Sender ID

What are the Sender ID requirements when sending SMS to recipients in Sri Lanka (+94)?

1. Organisations are encouraged to use their brand names as part of AlphaNumeric Sender IDs.
2. SMSs sent using Generic Sender IDs, including any variations of these (capitalised, lowercase or a combination) will be blocked. E.g, ALERT, Info, PassCode, etc

Best practice for choosing your Sender ID

Text.lk recommend this priority:

1. Use your brand
   Only use your company / organization or brand name.
2. Shorten the brand if necessary
   If the brand is: SuperTechSolutions use something like: SuperTech. rather than trying to fit the entire company name.
3. Keep it recognizable
   A customer / recipient should immediately know who sent the message.
4. Avoid unnecessary symbols
   Prefer: ABC Store. over: @ABC#Store!
5. Stay within 11 characters
   This is the hard limit for alphanumeric Sender IDs.

Using the Sender ID through the Text.lk API

Once your Sender ID has been approved, Text.lk’s API accepts it through the sender_id parameter.

Example:

{
  "recipient": "94710000000",
  "sender_id": "ABCStore",
  "type": "plain",
  "message": "Your OTP is 482931"
}

{
  "recipient": "94710000000",
  "sender_id": "ABCStore",
  "type": "plain",
  "message": "Your OTP is 482931"
}

The documented API limit for an alphanumeric Sender ID is 11 characters.

For new integrations, Text.lk recommends its OAuth 2.0/Bearer Token method rather than exposing the API token in a URL.

Text.lk SMS API documentation

Recommended rules for Text.lk Sender ID

If you’re creating your own Sender ID validation system, this is the practical rule set I’d use:

The key point is: for Text.lk, stick to a simple 1–11 character Sender ID using letters, numbers, spaces, -, or _, and get it approved before production use.

Send SMS with Text.lk

Text.lk provides SMS gateway services for businesses, developers, and organizations. Use the Text.lk platform and API to send OTPs, notifications, alerts, and other business SMS.