In this article I will explain with an example, how to implement GST Number validation using Regular Expression (Regex) in jQuery.
HTML Markup
The following HTML Markup consists of an HTML TextBox, SPAN and a Button.
GST Number:
<input type="text" id="txtGSTNumber" />
<span id="lblError" class="error">Invalid GST Number.</span>
<hr />
<input type="button" id="btnSubmit" value="Submit" />
Validating GST Number using Regular Expression in jQuery
Inside the jQuery document ready event handler, the Submit Button has been assigned a jQuery Click event handler.
When the Submit Button is clicked, the GST Number TextBox is referenced and its value is tested using a Regular Expression.
The following conditions must satisfy for a GST Number to be termed as valid.
1. It should be 15 characters long.
2. The first 2 characters should be a digit representing State Code.
3. The next 10 characters should be PAN number of the taxpayer.
Note: For more details on PAN Card Number validation, please refer my article PAN Card Number validation using jQuery and Regular Expression.
4. The 13th character should be any digit (1-9) or an alphabet.
5. The 14th character should be Z by default.
6. The 15th character should be an alphabet or any digit. 0-9.
Example: 06BZAHM6385P6Z2
<script type="text/javascript" src=""></script>
<script type="text/javascript">
    $(function () {
        $("#btnSubmit").click(function () {
            var regex = /^[0-9]{2}[A-Z]{5}[0-9]{4}[A-Z]{1}[1-9A-Z]{1}Z[0-9A-Z]{1}$/;
            if (regex.test($("#txtGSTNumber").val())) {
                $("#lblError").css("visibility", "hidden");
            } else {
                $("#lblError").css("visibility", "visible");
CSS Class
The following CSS classes are used.
1. error – It will apply RED color to the error message.
2. gst – It will force the letters to be UPPER case.
<style type="text/css">
    body { font-family: Arial; font-size: 10pt; }
    .error { color: Red; visibility: hidden; }
    .gst { text-transform: uppercase; }
GST (Goods and Services Tax) Number validation using jQuery and Regular Expression
Browser Compatibility

The above code has been tested in the following browsers.

Internet Explorer  FireFox  Chrome  Safari  Opera 

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